tag:blogger.com,1999:blog-64723337249584678962020-07-08T01:36:02.968-07:00PhysicsFMPhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.comBlogger36125tag:blogger.com,1999:blog-6472333724958467896.post-72014197321880205202020-05-02T17:39:00.001-07:002020-05-02T17:39:57.888-07:00Alain Aspect's Quantum Optics on Coursera<a href="https://www.amazon.com/Introduction-Quantum-Optics-Semi-classical-Quantized/dp/0521551129/ref=as_li_ss_il?dchild=1&keywords=alain+aspect&qid=1588454912&sr=8-1&linkCode=li1&tag=physicsfm00-20&linkId=91a2711ddfb11e2c37806e093e801a5a&language=en_US" target="_blank"><img border="0" align="right" src="//ws-na.amazon-adsystem.com/widgets/q?_encoding=UTF8&ASIN=0521551129&Format=_SL110_&ID=AsinImage&MarketPlace=US&ServiceVersion=20070822&WS=1&tag=physicsfm00-20&language=en_US" ></a><img src="https://ir-na.amazon-adsystem.com/e/ir?t=physicsfm00-20&language=en_US&l=li1&o=1&a=0521551129" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" />I finally got done with finals, and as a reward, I decided to see if I could find a <a href = http://www.coursera.org>Coursera</a> course to play with. I had been looking to see if there was a quantum computing MOOC available (and there are many), but among the search results was <a href = https://www.coursera.org/learn/quantum-optics-single-photon#syllabus>Alain Aspect's Quantum Optics</a> course on Coursera. This is, he says, the first of two MOOCs based on his textbook (at right*). It's a short course (4 weeks, basically four lectures), and so, just right for me.<br><br> The subject is interesting (and very similar to a special topics course I took as an undergraduate called "The Quantum Mechanics of the Laser" -- I wish I'd kept those notes when I moved), but the lectures are dense. They do go over a lot of the material in <a href = https://amzn.to/2z3NMBP>Sakurai's Modern Quantum Mechanics</a>*, which I worked through two summers ago, but of course with a focus on the meaning in terms of quantum optics. Already, some things I haven't heard of before, some that relate to experimental design (quantization volume), some straightforward interpretations of mathematical expressions (the energy of a single photon). The understand in terms of experimental parameters is particularly helpful to me (since I understand things in terms of experiments, due to my training).<br><br> The course, however, is not for those who are afraid of mathematics. Aspect's discussion in mathematically dense. Really dense. My students think I use too much mathematics in university physics classes, but this is all math. And Aspect expects you to have seen it all before: many times he references your prior knowledge. He doesn't quite say that you're an uneducated ignoramus if you can't recall trivialities like the photon energy or the uncertainty relations (he calls them dispersion relations, an aspect of his philosophy -- it's nice to hear an expert talk explain the mechanics of physics in a way that makes it clear he has opinions). And the homework is tough. Not as tough as it sounds when you read it, but pretty tough.[1] Even on the internet, you're expected to know your stuff.<br><br> <a href="https://www.amazon.com/Statistical-Mechanics-Algorithms-Computations-Physics/dp/0198515367/ref=as_li_ss_il?dchild=1&keywords=krauth&qid=1588465407&sr=8-2&linkCode=li1&tag=physicsfm00-20&linkId=da106d4d632051e389d1688c8ddb1843&language=en_US" target="_blank"><img border="0" align = right src="//ws-na.amazon-adsystem.com/widgets/q?_encoding=UTF8&ASIN=0198515367&Format=_SL110_&ID=AsinImage&MarketPlace=US&ServiceVersion=20070822&WS=1&tag=physicsfm00-20&language=en_US" ></a><img src="https://ir-na.amazon-adsystem.com/e/ir?t=physicsfm00-20&language=en_US&l=li1&o=1&a=0198515367" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" />I have found that I had to speed his lectures up. I don't know if it's him, if it's because he's European, or because Coursera makes everyone speak like someone shilling their latest book in a bad TED talk, but he talks slowly. Last summer, I took <a href = https://www.coursera.org/learn/statistical-mechanics>Werner Krauth's MOOC</a>,[2] from the same school but a different country, and he spoke with the same cadence. I found I had to speed up the lecture to 1.5x so that they spoke at a normal speed.<br><br> This minor technical problem aside, I certainly am enjoying the break this provides before I start preparing for my summer courses (How did I let myself get roped into summer courses? At least they're on-line so I can get a lot of the work out early).<br><br> [1] I didn't pay the $49.99, or whatever, it costs in order to get it graded, but I did work it. And it reinforced the advice I give to my students: try the homework before class, then the class will be more useful to you. [2] Which was serendipitous, since I'd begun setting up to work through the book it was based on, <a href = https://amzn.to/3dg79Xb>Statistical Mechanics: Algorithms and Computation</a>,* when Coursera sent me an e-mail about it. I get the feeling there's as much shilling on Coursera as there is at TED talks. But it couldn't be more: a TED talk is just an advertisement for a book. If you're lucky, there's more to the book than just the TED talk. Obviously, though, there's more to a physics textbook than eight hours of lecture. Hell, there's more to a physics textbook than the forty hours of lecture in a semester.<br><br> * Note: These links are to Amazon pages. Purchases on those pages from the links will give me a commission (at least for now -- every time I've tried to use the Amazon Associates program they've kicked me off for not selling anything, but I do like having the links in the show notes so that you can pick up the books we might reference in a discussion).PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-56133510172422078922020-04-22T08:28:00.003-07:002020-06-18T20:26:47.048-07:00Most Recent Podcasts<table><tbody><tr><td valign = top><strong><a href="frontiers.physicsfm.com">Physics Frontiers</a></strong><br /><br />Episode 51: <a href="https://physicsfm-frontiers.blogspot.com/2020/06/gravitational-wave-astronomy.html">Graviational Wave Astronomy</a><br /><br /><a href="http://physicsfm-master.blogspot.com/2017/09/physics-frontiers-index.html">All Physics Frontiers Episodes</a><br /><br /><a href="https://physicsfm-master.blogspot.com/2018/08/physics-frontiers-most-popular-episodes.html">Most Popular Physics Frontiers Episodes</a></td><td width="100"><br /></td><td valign = top><strong><a href="https://weeklyelectronicpaper.blogspot.com/">The Weakly Electronic Paper</a></strong><br /><br />Episode 4: <a href="http://papers.physicsfm.com/4">Entropy v. Entropy</a><br /><br /><a href="https://physicsfm-master.blogspot.com/2020/04/weekly-electronic-paper-index.html">More Episodes</a></td></tr></tbody></table><br /><br /><a href="http://physicsfm-master.blogspot.com/">Blog</a><br />Latest Blog Entry: <a href="https://physicsfm-master.blogspot.com/2020/05/alain-aspects-quantum-optics-on-coursera.html">Alain Aspect's Quantum Optics on Coursera</a><br /><br />Retired Podcasts:<br /><br />Quantum ParadoxesPhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-68194152738075028942020-04-22T08:21:00.002-07:002020-06-18T20:28:04.912-07:00Weekly Electronic Paper Index<a href="https://weeklyelectronicpaper.blogspot.com/">Podcast Home</a><br /><br />Posted Shows:<br /><br />4. <a href = https://weeklyelectronicpaper.blogspot.com/2020/06/entropy-v-entropy.html>Entropy v. Entropy</a> (2020/06/18)<br><br>3. <a href="https://weeklyelectronicpaper.blogspot.com/2020/04/uploaded-20200419-i-discuss-qbism-or.html">The Machine in the Ghost</a> (2020/05/13)<br /><br />2. <a href="https://weeklyelectronicpaper.blogspot.com/2020/04/itty-bitty-physics.html">Itty Bitty Physics</a> (2020/04/28)<br /><br />1. <a href="https://weeklyelectronicpaper.blogspot.com/2020/04/uploaded-20200419-i-discuss-qbism-or.html">The Quantum Bookie</a> (2020/04/19)<br /><br />PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-12764610231763152962018-09-01T10:07:00.002-07:002019-07-15T18:30:52.954-07:00Quantum Sense and Nonsense by Jean Bricmont<a href="https://www.amazon.com/Quantum-Sense-Nonsense-Jean-Bricmont/dp/3319652702/ref=as_li_ss_il?keywords=sense+and+nonsense+about+quantum&qid=1563240345&s=books&sr=1-1&linkCode=li2&tag=physicsfm0e-20&linkId=33ef12c646c13513f3211f5a1436b093&language=en_US" target="_blank"><img border="0" align = right src="//ws-na.amazon-adsystem.com/widgets/q?_encoding=UTF8&ASIN=3319652702&Format=_SL160_&ID=AsinImage&MarketPlace=US&ServiceVersion=20070822&WS=1&tag=physicsfm0e-20&language=en_US" ></a><img src="https://ir-na.amazon-adsystem.com/e/ir?t=physicsfm0e-20&language=en_US&l=li2&o=1&a=3319652702" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" />I don't really know why I picked up <a href = https://amzn.to/2lCbyOx>Quantum Sense and Nonsense</a> or when. I'm pretty sure it was in the last year when I was looking for some popular books to read after I finished <a href = http://physicsfm-master.blogspot.com/2018/05/the-wave-function-essays-on-metaphysics.html>The Wave Function</a>, and this one, written by Jean Bricmont and published by Springer, stood out. The cover, and likely the description, seems a little misleading since it seems to say that the book will focus on crazy and unfounded assertions of psychic and mystical properties attributed to quantum mechanics (and as Bricmont has published with Sokal, that's exactly what you'd think), but instead the book focuses on two experiments (double slit experiments and EPR-type experiments, both of which seem to be recurring themes on <a href = http://physicsfm-frontiers.blogspot.com/>Physics Frontiers</a>) and the interpretation of each. Bricmont follows Bell in asserting that EPR-experiments like the Aspect experiment show that there is some kind of non-locality at play in quantum mechanics and that the best way to interpret the meaning of the wave function (that is, what the wave function, itself, is) is to look toward an interpretation like the de Broglie-Bohm vision of the wave function (see Bell's, <a href = http://physicsfm-master.blogspot.com/2017/09/speakable-and-unspeakable-in-quantum.html>Speakable and Unspeakable in Quantum Mechanics</a>).<br><br> Despite being much different than what I thought the book would be, this made the Quantum Sense and Nonsense an excellent read.<br><br> The double slit experiment as performed by Thomas Young in the first decade of the 19th century showed that coherent light from the sun interfered with itself, showing that light is, in fact, a wave -- and brought about the belief in a mysterious Ether in which the light waves propagated. When Einstein showed the photoelectric effect requires quantization of light,* this made the interpretation more difficult. And de Broglie's prediction that electrons, really all material objects, have a wavelength and the subsequent discovery of electron diffraction, brought the same problem to all matter. And the interference is so strong that when a single photon or a single electron is sent through the slits, and the results of the experiments accumulated, the interference fringes are still seen. Material objects interfere with themselves. <br><br> A very strange property, and one that leads to many strange interpretations of quantum mechanics, is that if you set up a detector at one of the slits in the double slit experiment to see which slit the particle passes through, then the interference fringes will disappear. This leads to the idea that <I>observation</I> causes a change in the wave function, what is termed the wave function collapse. Many strange ideas come out of this, even from physicists (Bricmont's target). People use this idea to give consciousness a role in the measurement of quantum systems, Bricmont uses quotes from the following physicists to show the sloppy thinking on these points: d'Espagnat, Wheeler, and Mermin (to name only those I've heard of): they all give some role to the human mind in the collapse of the wave function. To be fair, understanding the collapse is impossible in the standard "Copenhagen" interpretation of quantum mechanics, which is what Schroedinger's cat was intended to show.<br><br> The EPR experiments, violations of Bell's theorem, are the second cause of sloppy thinking because they show one of two things: either (1) quantum mechanics is non-local or (2) quantum mechanics is non-causal. Those are the two assumptions that Bell uses to derive his inequalities beyond ordinary statistics and quantum theory. If you have to choose one of the two assumptions to invalidate, (1) is the more likely (although we recently published a podcast on <a href = http://physicsfm-frontiers.blogspot.com/2018/07/retrocausality.html>retrocausality</a> and Yakir Aharonov has a different version of a locality-preserving assumption, presented in his <A href = http://physicsfm-master.blogspot.com/2018/07/quantum-paradoxes-by-aharonov-and.html>Quantum Paradoxes</a> book as well as old papers). But once you remove locality from your assumptions about the world, people start babbling about telepathy and similar nonsense. <br><br> As befits someone of Bricmont's station, the descriptions of these experiments are exemplary, and Quantum Sense and Nonsense would be worth a read if only they were presented here. However, he does us another service by giving us a rich, logical and convincing description and defense of the de Broglie-Bohm pilot wave theory of quantum mechanics. In this theory, the wave and particle are broken up into two objects, an oscillation in space time that drives the motion of an otherwise deterministic particle. The randomness of quantum mechanics then ceases to be the mystical randomness associated with Bohr and Heisenberg and Copenhagen in general and becomes the deterministic randomness of statistical mechanics.** Bricmont goes so far to say that because of this and the fact that it can be mathematicised, de Broglie-Bohm is the only interpretation of quantum mechanics;*** the others (including statistical, Copenhagen, and many-worlds) don't meet that bar. Obviously, it doesn't mean that Bricmont is right, since he's delved into philosophy or worse in the comparison of interpretations by their linguistic characterizations, but it is a good way of thinking about the interpretations.<br><br> So I would recommend this book. I do think that it is a little too popular for most people that would read this, and he often refers to his own, more technical <a href = https://amzn.to/2k5gDOU>Making Sense of Quantum Mechanics</a> quite a bit for more quantitative details. He also says that this is only "slightly" more rigorous and would probably point you to P. Holland's <a href = https://amzn.to/2k4jTKn>The Quantum Theory of Motion</a> for a really rigorous treatment. I haven't read either of those two books, however, so I can't recommend them to you.<br><br>-------------------------------------------------------------<br><br>I wrote this review a little faster than I'd like because I'd just finished the book yesterday and Google sent me a "<a href = https://motls.blogspot.com/>news story</a>" on my phone today, which I read over my morning coffee. It was a rather infantile post by Luboš Motl, someone I've never heard of, who calls himself a "freelance string theorist" (but who has a reasonably impressive pedigree) reviewing books by science journalists. It makes me sad when a physicist does as bad a job of presenting science as a science journalist does.<br><br>The blog does a good job of showing two very bad ways to think about the interpretations of quantum mechanics. The first is from the book he reviews (or really, the blog post that he reviews of the book that it reviews). In that case, the science journalist author, whose name is of no importance, suggests that all interpretations are valid. This seems quite odd to me, especially when most of them are logically contradictory: if you believe in a wave function collapse, then you can't coherently believe in the universal wave function of Everett. You can make up a pretty complex and silly rationale if you want to, but it will always end up being incoherent somewhere (and I'm not going to read it to find out where). The reason you would want to hold multiple conceptions in your head is to find out places where they disagree -- and then to find an experiment that distinguishes them.<br><br> Motl himself presents to us the second version, which is to deny all interpretations. But that is clearly unsatisfactory. Although it is called the Copenhagen interpretation (by some, what is meant by that changes from philosopher to philosopher, physicist to physicist), you still have to have some interpretation. You have to have some ontological vision of the wave function to assert that information cannot travel faster than light during its collapse, for example, or to state that it would be impossible to ever use it for long distance communication. That you refuse to examine your beliefs doesn't mean that they're not there.<br><br> Bricmont does a good job of showing how to deal with interpretations without getting so dogmatic that his assertions become meaningless, just the opposite of Motl<br><br>------------------------------------------------------------ <br><Br> * Planck's experiments don't show this. Since the quantized electromagnetic waves are coming out of an enclosed chamber, black body radiation could be interpreted as having something to do with standing waves in the oven. <br><br> ** Interestingly, though, the roles of randomness are reversed. In statistical mechanics we measure macroscopic parameters associated with microstates. In quantum mechanics, and especially in the de Broglie-Bohm interpretation, the wave function is the microstate and the measurement is of the particle, or the microstate.<br><br> *** I should mention that de Broglie-Bohm is not excessively popular among physicists. Reading The Wave Function, however, I came out of it thinking it was extremely popular among professional philosophers of science.PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-27491114097370305842018-08-02T19:54:00.001-07:002020-05-24T16:15:26.548-07:00Physics Frontiers: Most Popular Episodes<b>All Time</b><br>1. Physics Frontiers 45: <a href = http://frontiers.physicsfm.com/45>Loop Quantum Gravity</a><br>2. Physics Frontiers 46: <a href = http://frontiers.physicsfm.com/46>Wigner's Friend</a><br>3. Physics Frontiers 44: <a href = http://frontiers.physicsfm.com/44> Spooky Action at a Distance</a><br>4. Physics Frontiers 38: <a href = http://frontiers.physcisfm.com/38>The Dimensionality of Space-Time</a><br>5. Physics Frontiers 1: <a href = hrrp://frontiers.physicsfm.com/1>The Graviational 4-Vector Theory of Carver Mead</a><br><br><br><b>2019</b><br>1. Physics Frontiers 45: <a href = http://frontiers.physicsfm.com/45>Loop Quantum Gravity</a><br>2. Physics Frontiers 46: <a href = http://frontiers.physicsfm.com/46>Wigner's Friend</a><br>3. Physics Frontiers 44: <a href = http://frontiers.physicsfm.com/44> Spooky Action at a Distance</a><br><br><br><b>2018</b><br>1. Physics Frontiers 38: <a href = http://frontiers.physcisfm.com/38>The Dimensionality of Space-Time</a><br>2. Physics Frontiers 33: <a href = http://frontiers.physicsfm.com/33>The String Theory Landscape</a><br>3. Physics Frontiers 40: <a href = http://frontiers.physicsfm.com/40>The Octonions</a><br><br><br><b>2017</b><br>1. Physics Frontiers 17: <a href = http://frontiers.physicsfm.com/17>The Physics of Time Travel</a><br />2. Physics Frontiers 9: <a href = http://frontiers.physicsfm.com/9>f(R) Theories of Gravity</a><br />3. Phyiscs Fronteirs 12: <a href = http://frontiers.physicsfm.com/12>A Graviational Arrow of Time</a><br /><br><br> <a href = http://fronteirs.physicsfm.com/>Physics Frontiers Index</a><br><br> [Edited 3/12/2020]PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-64480260962021720502018-07-25T20:10:00.003-07:002020-05-24T15:56:49.724-07:00Quantum Paradoxes by Aharonov and RohrlichYou might think I like <i>Quantum Paradoxes</i> [<a href="https://amzn.to/2yv35U1">Amazon</a>] by Yakir Aharonov and Daniel Rohrlich. I mean, I started a <a href="http://paradoxes.physicsfm.com/">podcast</a> about it. I might even finish it someday.*<br /><br /> This book explores the meaning of quantum mechanics through paradoxical thought experiments. It uses a few standard ones, like Schrodinger's cat, and a lot of interesting variations of the double slit experiment and electron diffraction. The first eight chapters motivate mainly how quantum mechanics works using paradoxes. The last ten chapters motivate Aharonov and Rohrlich's interpretations.<br /><br /><iframe align="right" frameborder="0" marginheight="0" marginwidth="0" scrolling="no" src="//ws-na.amazon-adsystem.com/widgets/q?ServiceVersion=20070822&OneJS=1&Operation=GetAdHtml&MarketPlace=US&source=ss&ref=as_ss_li_til&ad_type=product_link&tracking_id=physicsfm00-20&language=en_US&marketplace=amazon&region=US&placement=3527403914&asins=3527403914&linkId=7f74d9957d7ff23fbc7ac14fa870730e&show_border=true&link_opens_in_new_window=true" style="height: 240px; width: 120px;"></iframe>I am very enamored of the format.<br /><br /> Each chapter follows a formula. After a short preamble, a paradox is presented in detail. The paradoxes are presented as thought experiments, first. This means that a detailed, if not physically possible, experiment is described, and then its physics discussed. The physics leads to two possible interpretations, such as: there is no physical difference in the dynamics of an electron on either side of a charged capacitor, but quantum mechanics predicts a phase shift in the wave function of the electron. How can that be?<br /><br /> Next, aspects of the physics are discussed in mathematical detail. In this case, what is the relationship between the gauge and the phase of the wave function. This leads to a choice, clarification, or reconciliation. The most interesting part of this for me has been the use of modular variables to clear up some points that have to do with the use of gauges, although the general set-up of the interference experiments Aharonov and Rohrlich are discussing requires a bit of careful reading. Sometimes, a section or two follows with implications and real, physical experiments.<br /><br /> The second half of the book deals with the interpretation of quantum mechanics in the context of weak measurements. I really don't have a great idea about how to explain a weak measurement, but the two important facets are: (1) they allow you to measure the wave function without (completely) destroying it and (2) they are only approximations to the wave function. Aharonov and Rohrlich mainly deal with their own interpretation, and (a) the Copenhagen interpretation (a favorite among users of quantum mechanics) and (b) the many-worlds hypothesis (a favorite among string theorists). Mainly, I think, because these are their main competitors. <br /><br /> Their own interpretation has to do with temporal boundary conditions, which is very appealing to me because it's compatible with the block universe idea of relativity, at least conceptually. It's very important to remember that every fundamental physical theory must be compatible with every other fundamental physical theory -- if two theories that should apply to a situation don't, you have a paradox. So, any interpretation of quantum mechanics must be compatible with relativity. This hasn't been a problem with the theory -- quantum electrodynamics is exactly the integration of quantum mechanics and special relativity. It has been a major problem with interpretations, and the authors detail some of those problems in the book.<br /><br /> I don't want to go into more detail, but if you want to get more detail, then over the next thirty-four-odd weeks, I discuss each chapter with a friend of mine in a podcast. Contact me for the address if you're not already subscribed.<br /><br /> So, I just love this book. It's a great way to not only explore quantum mechanics, but to explore what it means to be an interpretation of quantum mechanics in a rigorous and technical, but not exceedingly technical (to a physicist). If you have the mathematical background to play with differential equations, or even the intellectual fortitude to not be scared of them, I highly recommend this book. If you don't have that knowledge, then check out the podcast. It'll probably be more than enough for you.<br><br> * Update (5/24/2020): To be clear here: I've read through the book three times, once to get ideas for teaching well before I'd started any podcast, once when Randy agreed to do the Quantum Paradoxes podcast, and finally, once when we started the podcst over. I think we've given up hope on finishing the <a href="http://paradoxes.physicsfm.com">Quantum Paradoxes</a> podcast. PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-65522901107015082452018-05-22T20:26:00.002-07:002020-05-13T19:53:00.719-07:00The Wave Function: Essays on the Metaphysics of Quantum Mechanics<br /><iframe style="width:120px;height:240px;" marginwidth="0" marginheight="0" align = "right" scrolling="no" frameborder="0" src="//ws-na.amazon-adsystem.com/widgets/q?ServiceVersion=20070822&OneJS=1&Operation=GetAdHtml&MarketPlace=US&source=ss&ref=as_ss_li_til&ad_type=product_link&tracking_id=physicsfm00-20&language=en_US&marketplace=amazon®ion=US&placement=019979054X&asins=019979054X&linkId=4de8e22e64cd79d67a336ac2f37462a2&show_border=true&link_opens_in_new_window=true"></iframe><br /><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";"><a href = https://amzn.to/3cwHwkO> The Wave Function</a> is a philosophy anthology about the wave function of quantum mechanics.<span style="margin: 0px;"> </span>The wave function specifies the state of the quantum mechanical system in a way similar to how the ideal gas law specifies the state of a dilute gas.<span style="margin: 0px;"> </span>You can make more or less of that, if you wish.<span style="margin: 0px;"> </span>But if you’re a philosopher, you’ll make more.</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">This book is not really about the wave function, what it does, and how to care for it, it is a discussion of David Albert’s thesis exposited in the 1996 paper, “Elementary Quantum Mechanics.”<span style="margin: 0px;"> </span>In this paper he looked the wave function as a real thing, and said that if it is real, then the universe must exist in 3N-dimensions, where N is the number of particles in the universe.<span style="margin: 0px;"> </span>This is because the wave function a system of particles is a collection of positions for those particles.</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">I’ll discuss each chapter in turn.<span style="margin: 0px;"> </span>You might think the description is a little short for some of them, but the review has gotten pretty long.</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">1. David Albert, “Wave Function Realism”</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">In this essay, David Albert of the philosophy department of Columbia University discusses his idea on how to view the wave function realistically.<span style="margin: 0px;"> </span>Realist, in the philosophical sense, of the wave function is a real thing, and so its nature can be used to tell us something about the nature of the rest of the world.</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">Since this is the view that most of the remainder of the essays discuss, and all address, it’s a good thing to go into detail about this here.<span style="margin: 0px;"> </span>If the wave function is a real, physical object, it is a kind of field.<span style="margin: 0px;"> </span>In physics, the word field refers to an object that can be represented as a function, which can be scalar, vector, or tensor-valued, that has different values at different points in space.<span style="margin: 0px;"> </span>The velocity field of a stream, for example, is a vector field that tells you how fast and in what direction the water in that stream is moving at that point.<span style="margin: 0px;"> </span>In a steady state, even though the water is different at every instant, the current is the same at every point.<span style="margin: 0px;"> </span>Its domain is the physical, three dimensional space that composes the stream (technically, it could be all space), and its range is the three dimensional velocity vectors that the water can travel at (magnitudes and directions.</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">What Albert noticed is that the domain of the field is, in all of physics, the 3D space that we live in or a subset of it.<span style="margin: 0px;"> </span>All of physics, that is, except in quantum mechanics, where the domain of the wave function is the possible positions of each of the particles that the wave function describes (is that true?*), and so instead of being a 3-dimensional space, it is a 3N-dimensional space with N being the number of particles.<span style="margin: 0px;"> </span>Albert’s leap was to say that since quantum mechanics is the foundational theory of the world, this 3N-dimensional space is the REAL world whereas our usual 3-dimensional space is an apparition based on the relationships between large number of particles.</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">The reason why we don’t see the 3N world is basically a brain-in-a-vat type of problem.<span style="margin: 0px;"> </span></span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">2. Valia Allori, “Primitive Ontology and the Structure of Physical Theories”</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">Valia Allori, a philosopher at Northern Illinois University, tries to understand all this in a very philosophical way.<span style="margin: 0px;"> </span>She invents sub-categories within categories that you’d never heard of.<span style="margin: 0px;"> </span>In this case, she starts talking about the “primitive ontology” of a theory.<span style="margin: 0px;"> </span>This is all, if I recall, along the same program as Albert.<span style="margin: 0px;"> </span></span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">An ontology in the philosophy of science is the collection of thing in the world on which the theory can function, whether they be atoms or charges or point particles.<span style="margin: 0px;"> </span>A primitive ontology is the minimum ontology for the theory to function.<span style="margin: 0px;"> </span>This varies from theory to theory, and it has a set of “primitive variables” which create the minimum parameterization that allows you to translate the objects of the primitive ontology into mathematics.</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">Allori analyzes three and a half theories with this system: Bohmian mechanics, the Ghirardi-Rimini-Weber (2x versions), and the many-worlds interpretation.<span style="margin: 0px;"> </span>These three interpretations keeps coming up, and not very many more, so I wonder if most of the philosophy of quantum mechanics is a detailed response to John Bell, especially the collection The Speakable and Unspeakable in Quantum Mechanics – since those were, really the three that he detailed in that book.</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">3. Steven French , “Whither Wave Function Realism”</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">Steven French, a philosopher at the University of Leeds, wonders whether the wave function is the right thing for the realist philosopher of science to consider as part of the ontology of the theory.<span style="margin: 0px;"> </span>He feels that overestimating the importance of the wave function in using quantum mechanics to tell us about the world underdetermines the theory and leaves us with a rather vague idea about what really exists.</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">4. Sheldon Goldstein and Nino Zanghi, “Reality and the Role of the Wave Function in Quantum Theory”</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">Sheldon Goldstein, a mathematician at Rutgers, and Nino Zanghi, a physicist at the University of Genoa,<span style="margin: 0px;"> </span>wonder just what it is that a wave function can be, and there are several things that look at.<span style="margin: 0px;"> </span>First of all, there can be no such thing as the wave function in the world.<span style="margin: 0px;"> </span>It is just a computational tool.<span style="margin: 0px;"> </span>Next, it could be an epistemic representation of our subjective knowledge of the system.<span style="margin: 0px;"> </span>That is, it isn’t physical but it has something to do with the state of something physical – basically, the state of our brains.<span style="margin: 0px;"> </span>Or it can be some fact or object in the world – a thing in the world.<span style="margin: 0px;"> </span>That it, the wave function could be nothing, it could be epistemic, or it could be real.</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">The main point of most of these papers is to analyze and criticize Albert’s wave function realism, so it is the last that is interesting.<span style="margin: 0px;"> </span>If the wave function is real, there are two possibilities: it could be nomological or material, or at least partially one or the other will a little subjectiveness or nothingness thrown in.<span style="margin: 0px;"> </span>If it is nomological, it is a fact about the world, like Gauss’ Law.<span style="margin: 0px;"> </span>If it is material, it is a real thing, like a changed pith ball.<span style="margin: 0px;"> </span>But again, they give themselves a little wiggle room by allowing the wave function to be either quasi-nomological or quasi-material.<span style="margin: 0px;"> </span>It might be factish or thinglike.<span style="margin: 0px;"> </span></span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">Just like the Allori paper, Goldstein and Zanghi analyze a group of different interpretations of quantum mechanics to determine what role the wave function plays in each according to this categorization.<span style="margin: 0px;"> </span>If you’re interested enough in which is what and what is which, you’re probably interested enough to read the book, so I’ll save myself some time and not make out a table.</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">5. Peter Lewis, “Dimension and Illusion”</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">Peter Lewis, a Dartmouth philosopher that was at the University of Miami when The Wave Function was published, gives a pragmatic analysis of Albert’s thesis.<span style="margin: 0px;"> </span>And it’s no surprise what a pragmatist will think about a 3N-dimensional world.</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">6. Tim Maudlin, “The Nature of the Quantum State”</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">Time Maudlin, New York University Philosopher, provides the most direct assault on Albert in this book.<span style="margin: 0px;"> </span>That is, he goes after the main method of analysis – producing an ontology from the mathematics – in order to show that 3N-dimensional space isn’t necessary.<span style="margin: 0px;"> </span>He does this both by careful analysis of Alberts 1996 paper and with an analogy to Fourier’s Analytical Theory of Heat, which provided a metaphysical cover for the caloric fluid model of heat.</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">That particular induction was natural.<span style="margin: 0px;"> </span>The equations in the theory of heat flow are the same as those as for current flow in liquids.<span style="margin: 0px;"> </span>So, if you don’t have any idea about statistical mechanics, it’s the most natural thing in the world to see heat as a current of some sort of fluid instead of just energy transfer.</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">And of course, that didn’t work.</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">Maudlin’s conclusion is justified: looking at the mathematical form that a theory has to take does not require you to take implications of the mathematics to be real – to be in the ontology of the theory, as the philosophers put it. <span style="margin: 0px;"> </span>Not only is not necessary, it’s not even a good reason.</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">7. Bradley Monton, “Against 3N-Dimensional Space”</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">Bradley Monton, who worked at the University of Colorado at Boulder at the time but now philosophizes at Wuhan University, sets the tone for this one with his first section “Quantum Mechanics is False.”<span style="margin: 0px;"> </span>Why does he say that? Because he feels that General Relativity is the more fundamental theory of the two, mostly because quantum mechanics synchronize their watches.<span style="margin: 0px;"> </span>This may seem trivial, but it’s a major problem in using string theory to construct a theory of gravity.</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">His main argument against the 3N-dimensional space and in favor of 3-dimensional space as being the fundamental dimensionality of the world is that 3-dimensional space more accurately reflects what physicists think about the world and how they carry out experiments.<span style="margin: 0px;"> </span>And, Monton argues, unless 3N-dimensional space can make itself useful, then there’s no good reason to take it as fundamental.</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">8. Alyssa Ney, “Ontological Reduction and the Wave Function Ontology”</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">Alyssa Ney, a philosopher at the University of California at Davis, gives an account of “ontological reduction,” how one set of things can be reduced to another set of things.<span style="margin: 0px;"> </span>In this case, she gives an account of how our 3-dimensional experience can reduce to the 3N-dimensional space of the wave function.<span style="margin: 0px;"> </span>You can think of this in analogy to scientific reductionism where biology can be reduced to chemistry, for example, for a certain idea about what biology is.<span style="margin: 0px;"> </span>Chemistry never gives you the full picture of biology, but we have faith that between chemistry and physics, everything about living things can be explained in some reasonable way – although not predicted.</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">9. Jill North, “Structure of the Quantum World”</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">Jill North, now of Rutgers, once of Cornell, discusses how Albert’s program is supported by the dynamics of the world.<span style="margin: 0px;"> </span>If the wave function changes in 3N-dimensions, then a 3N-universe is the best explanation of it.<span style="margin: 0px;"> </span>I didn’t see it before, but I see it now: North’s view of the wave function is of the universal variety, and the universal wave function is the most physical assumption of the many-world’s hypothesis.</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">10. David Wallace, “A Prolegomenon to the Ontology of the Everett Interpretation”</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">David Wallace moved from Oxford to the University of Southern California to do his philosophizing.<span style="margin: 0px;"> </span>Here, he talks a lot about the many-worlds interpretation.</span></div><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";"><span style="margin: 0px;"> </span>* In the case of identical particles, the wave function gives the probability amplitude of finding *a* particle there.<span style="margin: 0px;"> </span>It doesn’t tell you which one.</span></div>PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-18031846620083602982018-04-25T19:34:00.000-07:002018-09-01T13:07:30.047-07:00Book Review Index<ol><li><a href = http://physicsfm-master.blogspot.com/2018/09/quantum-sense-and-nonsense-by-jean.html>Qunatum Sense and Nonsense</a> by Bricmont</la><li><a href = http://physicsfm-master.blogspot.com/2018/07/quantum-paradoxes-by-aharonov-and.html>Quantum Paradoxes</a> by Aharonov and Rohrlich</li><li><a href = http://physicsfm-master.blogspot.com/2018/05/the-wave-function-essays-on-metaphysics.html>The Wave Function: Essays on the Metaphysics of Quantum Mechanics</a>, Ney and Albert, Eds.</li><li><a href= http://physicsfm-master.blogspot.com/2018/04/cosmic-update-by-adams-buchert-and.html>Cosmic Update</a> by Adams, Buchert, and Mersini-Houghton </li><li><a href = http://physicsfm-master.blogspot.com/2018/03/the-nature-of-space-and-time.html>The Nature of Space and Time</a> by Hawking and Penrose</li><li><a href =http://physicsfm-master.blogspot.com/2017/10/extra-dimensions-in-space-and-time-by.html>Extra Dimensions in Space and Time</a> by Bars and Terning</lI><li><a href = http://physicsfm-master.blogspot.com/2017/09/theory-and-experiment-in-gravitational.html>Theory and Experiment in Gravitational Physics</a> by Will </li><li><a href = http://physicsfm-master.blogspot.com/2017/09/speakable-and-unspeakable-in-quantum.html>Speakable and Unspeakable in Quantum Mechanics</a> by J.S. Bell</li> </ol>PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-67402007897480838072018-04-24T11:22:00.001-07:002018-07-28T19:46:40.602-07:00Cosmic Update by Adams, Buchert, and Mersini-Houghton<a href="https://amzn.to/2Aj2G7v">Cosmic Update: Dark Puzzles, Arrow of Time, Future History</a> is the second book in the <a href="http://www.mvjs.org/">Multiversal Journeys</a> series run by <a href="https://fqxi.org/grants/large/awardees/view/__details/2006/nekoogar">Farzad Nekoogar</a> and published through Springer. Like its predecessor in the series, <a href="http://physicsfm-master.blogspot.com/2017/10/extra-dimensions-in-space-and-time-by.html">Extra Dimensions in Space and Time</a>, this is an accessible, semi-technical discussion about different matters in theoretical physics by experts. In this case, the three main essays are about cosmology, especially: if the universe is expanding due to an unidentifiable force, what does that mean about our physics. All of these topics are perfect topics for Physics Frontiers, and some probably have been and will be.<br /><br /><a href="https://www.amazon.com/Cosmic-Update-Puzzles-Multiversal-Journeys/dp/1489994130/ref=as_li_ss_il?_encoding=UTF8&me=&qid=1532832262&linkCode=li2&tag=physicsfm0a-20&linkId=750c6b9da193785137b811cd5ecd66f8&language=en_US" target="_blank"><img border="0" align = right src="//ws-na.amazon-adsystem.com/widgets/q?_encoding=UTF8&ASIN=1489994130&Format=_SL160_&ID=AsinImage&MarketPlace=US&ServiceVersion=20070822&WS=1&tag=physicsfm0a-20&language=en_US" ></a><img src="https://ir-na.amazon-adsystem.com/e/ir?t=physicsfm0a-20&language=en_US&l=li2&o=1&a=1489994130" width="1" height="1" border="0" align = right alt="" style="border:none !important; margin:0px !important;" />The first essay, "Dark Energy and Dark Matter Hidden in the Geometry of Space?" by Thomas Buchert describes how gravitational theory is being modified to accommodate the expansion of the universe. In particular, it describes the attempt to look at how the structure we see in the universe aids in creating an apparent cosmological constant. Standard cosmology usually assumes uniform values for the energy density and pressure of the universe, although we know that to be untrue. It's "true enough," they say, "on average." Buchert and coworkers have been looking at how that average model breaks down in the presence of known structure, and what the implications of that structure are, and apparently those nonuniformities might account for the dark energy field and dark matter halos observed by astronomers. The process that does this is the gravitational backreaction against cosmic evolution. Exactly how this works, I'd need to delve into, but it's an interesting way to model what's happening to the cosmos that gives a physical explanation to some ghostly phenomena.<br /><br />The second essay, "The Arrow of Time in a Universe with a Positive Cosmological Constant Λ" by Laura Mersini-Houghton identifies the direction of thermodynamic processes based on the expansion on the universe. And what apparently happens is that in a de Sitter universe, the gravitational entropy eventually exceeds the matter entropy, and time reverses. Worse, when it happens, there is a "tachyonic instability" from (or by?) "super-Hubble" modes, which results in a violent transition at the boundary. At the conclusion of the chapter Mersini-Houghton says that the result of her theoretical inquiry into the direction of time is that we cannot have a "pure" Λ for dark energy, the cosmological constant has to vary in space and time, in order to avoid a breakdown of general relativity in the infrared regime.<br /><br />The last of the original essays, "The Future History of the Universe" by Fred Adams is an updated physical eschatology accounting for the presence of dark energy. He discusses the fate of stars of different sizes, black holes, and so on. It's entropically depressing, of course. The universe is young now, in its "stellariferous" era with its fancy stars and pretentious galactic clusters, but in the long run, it's going to be a bleak, black place. In just another 10<sup>33</sup> years, though, the universe will be quite unfashionable and enter into the degenerate era, full of brown dwarfs, white dwarfs, blue dwarfs, and any other dwarf that found a way to get out. The scary, lonely thing is that some of these blue dwarfs will have habitable worlds. But there won't be anything out there in the sky for them to see. Going over my notes, I didn't really get where the changes were, except that there were supposed to be difference from what you'd have read in 1995, but it is an interesting discussion.<br /><br />An added bonus is a reprint of a paper by Lawrence Krauss and Robert Scherrer, "The Return of the Static Universe and the End of Cosmology" that supplements the last essay by saying that there will be a point in future where an observer will not be able to tell that the universe is expanding.<br /><br />All in all very interesting. It's a little expensive, unlike the next book in the series, <a href="https://amzn.to/2K9osLA">Quantum Physics, Mini Black Holes, and the Multiverse: Debunking Common Misconceptions in Theoretical Physics</a> (just out) but if you can get a copy, it's worth a read.PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-67413490980404286802018-03-16T20:31:00.000-07:002020-05-14T06:08:35.408-07:00The Nature of Space and Time by Hawking and PenroseStephen Hawking died two days ago, and I have a copy of <I><a href = https://amzn.to/2Lv463Z>The Nature of Space and Time</a></I> sitting in my review pile waiting its turn. It doesn't have to wait its turn, though, because (1) Stephen Hawking recently died, and so it would be nice to review something of his as a homage, and (2) It's short and so easy to review.<br><br><a href="https://www.amazon.com/Nature-Space-Newton-Institute-Lectures/dp/069116844X/ref=as_li_ss_il?s=books&ie=UTF8&qid=1532832415&sr=1-1&keywords=the+nature+of+space+and+time&linkCode=li2&tag=physicsfm0a-20&linkId=de85e6f204c50db639cd498881b06141&language=en_US" target="_blank"><img border="0" align = right src="//ws-na.amazon-adsystem.com/widgets/q?_encoding=UTF8&ASIN=069116844X&Format=_SL160_&ID=AsinImage&MarketPlace=US&ServiceVersion=20070822&WS=1&tag=physicsfm0a-20&language=en_US" ></a><img src="https://ir-na.amazon-adsystem.com/e/ir?t=physicsfm0a-20&language=en_US&l=li2&o=1&a=069116844X" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" />The premise of the book is that it is a series of lectures by Hawking and his mentor Roger Penrose. This was "the high point of a six month program held in 1994 at the Isaac Newton Institute for Mathematical Sciences at the University of Cambridge." I'm not sure where Cambridge is or what it's famous for, but I'm sure this was the hottest thing going in that half-year. The book itself is not a debate, only the last of the seven chapters. The first six are lectures alternately by Hawking and Penrose building up to the debate. If the seventh lecture was the high point of the program, the lectures certainly built up the dramatic tension in exactly the way universities don't build up dramatic tension.<br><Br>The lectures are semi-non-technical. By that I mean that Hawking and Penrose can't help themselves and they put the pretty equations in the text for you to admire, but they aren't used for anything. So, really, they're nothing more than window dressing for the topic at hand. The topics are the classical theory of space and time (what is the future, what is the past, do they always exist?), singularities in space time (and some ideas about them), many varieties of quantum mechanical stuff (quantum black holes, quantum cosmology, quantum gravity), and twistor theory. Not necessarily light subjects, but presented in a way that most anyone should be able to understand.<br><br>And here both Hawking and Penrose get a chance to discuss some of their theories, like: why, exactly, would nature abhor a singularity? How exactly does it go about hiding them?<br></br>To be honest, the debate doesn't seem to be very heated when you get to it. It's just a restatement of the positions outlined beforehand, mostly. Not much "here's why I'm right and you're wrong." So, if you were waiting to find out who won the debate, I'm sorry: it wasn't that kind of debate.<br><Br> ----------------------------------------------------- I just noticed that Princeton is now putting this is a series call "The Isaac Newton Institute Series of Lectures," which is awesome. I want to read all of the books in that series. It's just that I have: there's only one in it so far, and that's this one -- which I read in its old Princeton Science Library format (a series that I love)<br><br> I'm sure the Isaac Newton Institute has brought some very engaging speakers in, and I was wondering if you'd help me bother them for more.<br><br>Mostly for myself, what I'm thinking about reading:<br><ul><li><a href = http://amzn.to/2G3rKkn>Quantum Physics, Mini Black Holes, and the Multiverse: Debunking Common Misconceptions in Theoretical Physics (Multiversal Journeys) by Yasunori Nomura (Author), Bill Poirier (Author), John Terning (Author), Farzad Nekoogar (Editor) </a></li><li><a href = http://amzn.to/2HGTIQe>Quantum Sense and Nonsense</a> by Jean Bricmont</li><li><A href = http://amzn.to/2FG175y> Quantum-Classical Analogies (The Frontiers Collection) by Dragoman and Dragoman</a><a href = https://amzn.to/2GxjlXn>A</a> [started, actually, 7/28/2018] </ul>PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-88366696135300405822018-01-22T09:56:00.001-08:002018-02-15T07:41:38.005-08:00StubThis is a stub for show notes.<br /><br />The link you're looking for will be redirected to the show notes for the episode you're interested in as soon as it is about 50% ready.<br><br>Until then, go <a href =http://physicsfm-master.blogspot.com/2017/09/physics-frontiers-index.html>HERE</a> for an index of all Physics Frontiers shows.PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-50469557889003746362017-11-12T17:45:00.001-08:002017-11-12T17:45:17.452-08:00Video: Physics Frontiers Episode 2Finally got a video together for Physics Frontiers 2 - The de Broglie - Bohm Interpretation of Quantum Mechanics. It's available on YouTube: <a href = https://youtu.be/Y0PBlvfrVbE>PhysicFrontiers0002.mp4</a> Tell me what you think. I'm trying to add some illustrations that I think might be helpful. PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-41064185527885717982017-10-31T19:53:00.000-07:002017-10-31T19:53:11.449-07:00Happy Birthday, Physics FrontiersPhysicsFM was 3 years old October 20th, and the first Physics Frontiers episode came out one year ago today!<br /><br />We've had over 20,000 downloads in our first year, plus almost 3,000 embedded plays through Podomatic.<br /><br />Thank you for listening to our podcast. Randy and I are just a little bit happier every time you play one of our podcasts, and twice as happy every time you share it with a friend!<br /><br />Thanks again!<br /><br />JimPhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-85404807727193470872017-10-17T12:00:00.000-07:002018-07-29T08:26:24.090-07:00Extra Dimensions in Space and Time by Itzhak Bars and John Terning<a href="https://amzn.to/2K4GopB"><i>Extra Dimensions in Space and Time</i></a> is a wonderful find. A few months ago, Randy and I talked about Itzhak Bars' 2T theory of space and time for a <a href="https://physicsfm-frontiers.blogspot.com/">Physics Frontiers</a> podcast (it's two podcasts up in the editing queue and will come out about a month from when I publish this), and it was one of the hardest this for us to get a handle on. Randy is really excited about Bars' theory (and not just because he went to USC), but reading the papers he selected left us a little confused about how it worked. When I saw that Springer had a book by Bars on the subject, I decided to take the $125.00 hit. Maybe a longer form text would help me figure out what was going on, and maybe choose a couple of different papers for another podcast that were a little more understandable.<br /><a href="https://www.amazon.com/Extra-Dimensions-Space-Multiversal-Journeys/dp/0387776370/ref=as_li_ss_il?s=books&ie=UTF8&qid=1532877907&sr=1-1&keywords=extra+dimensions+in+space+and+time&linkCode=li2&tag=physicsfm0a-20&linkId=174f2d332da4314a52e757e9301fca06&language=en_US" target="_blank"><img border="0" align = right src="//ws-na.amazon-adsystem.com/widgets/q?_encoding=UTF8&ASIN=0387776370&Format=_SL160_&ID=AsinImage&MarketPlace=US&ServiceVersion=20070822&WS=1&tag=physicsfm0a-20&language=en_US" ></a><img src="https://ir-na.amazon-adsystem.com/e/ir?t=physicsfm0a-20&language=en_US&l=li2&o=1&a=0387776370" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /><br />And I was pleasantly surprised by this book.<br /><br /><i>Extra Dimensions in Space and Time</i> is the first in the <i>Multiversal Journeys</i> series, edited by Farzad Nekoogar. This series of books is fulfilling the purpose of the <a href="http://www.mvjs.org/">Multiversal Journeys</a> organization:<br />making theoretical physics easy for the public. In that, the two halves of this book are non-technical introductions to their topics. The first hundred pages, by Itzhak Bars, talks about a theory of particles and interactions that uses two different time-like dimensions. The next sixty pages, by John Terning, discusses what the proliferation of spatial dimensions in string theory means. And they don't hurt your brain.<br /><br />In Itzhak Bars' "Two-Time Physics: The Unified View from Higher Dimensional Space and Time," Bars discusses the reasons for his 2T physics. This includes an insightful development of physics, including string theory itself, building up to the rationale for the second time dimension. And then he discusses the implications of the theory.<br /><br />Interestingly, two-time physics was the result of Bars' postulation of a symmetry. His postulate is this: there is a phase-space symmetry between different space-time dimensions without affecting the physics. Any particular direction at any particular event can be swapped with any other. Furthermore, this works with the energy-momentum tensor. On top of that, an energy can be swapped with a time and a spatial dimension can be swapped with a momentum component. Although his figure does not include cross arrows, I'd expect this to be true with the other possible reconfigurations. He calls this the Sp(2,R) symmetry.<br /><br />Again, physics does not change when you regard a spatial dimension as being time-like, as long as you switch a time dimension to be space-like.<br /><br />If this symmetry is indeed a law of nature, like translational or rotational symmetries, then there must be two time dimensions (no more and no less) and four space dimensions (at least, maybe you can have more, I don't remember, but you can't have less) to prevent anomalies like ghost particles -- the real universe is the 4+2 universe. These two extra dimensions are macroscopic, not the microscopic curled-in dimensions of string theory. And this leads to all of the interesting physics. The big, interesting analogy is that the universe you and I reside in, the 3+1 universe, is a holographic shadow of the 4+2 universe. And it is the way in which 4+2 objects project into 3+1 space-time that determines how we view them. <br /><br />The eight ways in which Bars had shown these objects to project into our space are as:<br /><ol><li>Dirac Particles </li><li>Particles in a Robertson-Walker Universe</li><li>Massive Particles</li><li>Particles in Maximally Symmetric Spaces</li><li>The Hydrogen Atom</li><li>Particles in a Conformally Flat Space</li><li>The Harmonic Osciallator</li><li>Twistors</li></ol><div>which isn't everything, but its a lot.</div><div><br /></div><div>Bars claims for 2T-Physics are the following:</div><ol><li>Sp(2,R) gauge symmetry of phase space is a fundamental property of nature.</li><li>2T-field theory, free of ghosts, has be successfully constructed and applied.</li><li>Grand unified theories and supersymmetric 2T-field theory have been constructed as 2T-field theories.</li><li>2T-physics provides new technical computation tools for 1T-physics.</li><li>2T supergravity, 2T strings, 2T branes, 2T M-Theory are only partially constructed in 2T-physics at this time.</li><li>A deeper phase space formulation of field theory is likely to exist.</li><li>The extra space and time dimensions in 2T-physics are neither small nor hidden.</li></ol><div>John Terning's "Extra Dimensions of Space" is of a similar level, if not anywhere near as weird. This is because Terning focusses on the strings and branes in M-Thoery, and stays just as far away from the scary math, ending, more-or-less, at the Higgs. When the book was written, in 2009, the Higgs particle hadn't been discovered at the LHC, but it was expected. Although nowhere near as detailed and nowhere near as out there as Bars' discussion, Terning does a good job of explaining why you need something like a string theory, and why the string theories that are limits of M-Theory satisfy those issues. </div><div><br /></div><div>He builds up from the standard modern physics story, through symmetry and gravity, and then discusses string theory. How do strings manifest as particles? How do they interact with each other and with branes? How do branes deform, and what are the implications of such a deformation? Those are the questions Terning answers, just a little bit more exactly than you're used to in an equation-free account.</div><div><br /></div><div>There is also a final chapter for those of you who feel like equation-free is to physics as Diet Pepsi is a Coca-Cola, "The Equations behind the Words." The thing is, I expect that for most of you that are interested in the exactness that mathematics provides a concept, the equations provided are things you're already familiar with.</div><br />But since that's the 13th chapter, you're going to skip it anyway.<br /><br />So, this is a great book, especially given my expectations from Bars' papers, and I recommend it to people who want a deeper understanding about the theories that require additional dimensionality for the world. It's a step up from a popular book, and I think it's exactly the sort of thing that someone who listens to our podcast to enjoy.PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-7984938208026638422017-10-07T10:37:00.000-07:002017-10-07T10:38:10.524-07:00Stochastic Electrodynamics<iframe src='https://podomatic.com/embed/html5/episode/8582858?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br /><br />Is the entire cosmos awash in a sea of invisible energy? Nikola Tesla thought so. And today a few daring theoretical physicists are pioneering the effort to explain the most exotic characteristics of quantum theory by describing the nature of this universal field of energy and its physical consequences. If they’re right, their theory could revolutionize the energy and transportation sectors around the globe, and perhaps even throw open the door to new forms of spaceflight. On this episode of Physics Frontiers, we’ll investigate the theory of stochastic electrodynamics, one of the most intriguing concepts in modern physics and a rising contender to explain the quantum world. <br /><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The main paper we read for this program: <a href="https://arxiv.org/abs/quant-ph/0501011v2">Contribution from Stochastic Electrodynamics to the Understanding of Quantum Mechanics</a> by de la Peña and Cetto <a href="https://arxiv.org/abs/quant-ph/0501011v2">[arXiv]</a> <br />2. The secondary paper we mentioned in program, predicting spontaneous parametric up-conversion: <a href="https://arxiv.org/abs/quant-ph/0203042v1">Non-Locality: The Party May Be Over</a> by Marshall <a href="https://arxiv.org/abs/quant-ph/0203042v1">[arXiv]</a> <br /><br />3. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-31254730156262440122017-09-24T15:38:00.004-07:002020-07-02T09:11:20.605-07:00Theory and Experiment in Gravitational Physics by Clifford M. Will<a href="https://amzn.to/2YrkBTK"><i>Theory and Experiment in Gravitational Physics</i></a>* is an excellent, if old, tract on the confrontation of general relativity and experiment (I read the revised edition of 1993). The author, C. M. Will, however, gives regular updates in the literature (the last time was <a href="https://link.springer.com/article/10.12942/lrr-2014-4">2014</a>, to my knowledge). The theme of the book, really, is that General Relativity works and that, for the most part, its alternatives don't. At least not very well.<br /><br /><a href="https://www.amazon.com/Theory-Experiment-Gravitational-Physics-Clifford/dp/1107117445/ref=as_li_ss_il?s=books&ie=UTF8&qid=1532878158&sr=1-3&keywords=theory+and+experiment+in+gravitational+physics&linkCode=li2&tag=physicsfm00-20&linkId=04e15f123d4d5d9a7339c8fcc2fa46b2&language=en_US" target="_blank"><img border="0" align = right src="//ws-na.amazon-adsystem.com/widgets/q?_encoding=UTF8&ASIN=1107117445&Format=_SL160_&ID=AsinImage&MarketPlace=US&ServiceVersion=20070822&WS=1&tag=physicsfm00-20&language=en_US" ></a><img src="https://ir-na.amazon-adsystem.com/e/ir?t=physicsfm00-20&language=en_US&l=li2&o=1&a=1107117445" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" />This isn't to say that Will shortchanges alternative theories. In fact, I'd say the opposite. Will depicts a wide array of theories of gravity, mainly of the "metric theory" variety because only metric theories of gravity seems to be consistent with experiment -- and the Einstein Equivalence Principle (he hints that the earlier edition included more, and in a few places he includes more). A metric theory satisfies three postulates:<br /><ol><li>The underlying space-time structure is defined by a metric tensor field.</li><li> The world lines of small objects are geodesics in space.</li><li> The local space-time geometry approximates a Minkowski space.</li></ol>If you've worked with general relativity in the past, you were working with a metric theory of gravity. It sounds like this would be an extremely restrictive culling of theories, but it turns out that there were already a large number of such theories of gravity being explored in the 1980's. And if you read the update, you'll find more (including the f(R) theories). Every one of these theories needs to have a tensor metric like general relativity, but they differ in having secondary gravitational fields, sometimes of quite different character (scalar, vector, or tensor), which changes the way in which matter couples to the metric...and therefore produce measurable differences in how space-time responds to the presence of physical objects.<br /><br />The tests are presented in various ways. <br /><br />There is an early description of tests of the Einstein equivalence principle (which states that a small object will follow a geodesic trajectory), since that eliminates all non-metric theories. The most important such test is the Eoetvoes experiment, which is a Cavendish-like experiment with bodies of different compositions; if this acts just like the Cavendish experiment, then the weak equivalence principle is sound. And that is about a third of what you need to show that the Einstein equivalence principle is sound. The other two points are local Lorentz invariance, which is tested by the Hughes-Drever NMR experiment, and local position invariance, which is tested by gravitational red shift experiments. These tests restrict gravity to be a metric theory.<br /><br />Since only metric theories are valid, Will then discusses a parameterized post-Newtonian framework for stellar system tests of gravitational theories. By performing perturbative expansions of the dynamical quantities in the various gravities, he creates a suite of parameters that describe how gravity changes near bodies that are just a little more massive than can be described by classical physics. Each metric theory has a range for each of these parameters in which it is viable. So when measurements are taken, these parameters can be calculated by the data and then used to put limits on, and in some cases disqualify, theories of gravity. Furthermore, many of these parameters indicate symmetry and conservation laws that are valid or invalid in the theory. So even if a theory is not ruled out by experiment, this formulation tells you if, say, the law of conservation of angular momentum holds in it.<br /><br />Getting to this point is essentially the first half of the book, and the second half mainly describes how different theories fare when confronted with the physical world.<br /><br />His first foray is into what he calls the classical tests of general relativity, which he modifies because the gravitational red shift experiment is really a test of the weak equivalence principle. So he swaps that out, and uses the deflection of light, the time-delay of light, and the perihelion shift of Mercury as his tests. He then worries about tests of the strong equivalence principle -- which is very like the Einstein equivalence principle, but self-gravitating bodies cannot react to their own effects on space. He finishes up with tests of gravity waves (which oscillate differently in different theories of gravity), binary pulsars (whose neutron stars should be dense enough to affect their own trajectories, if such a things is possible), and a variety of cosmological tests (this was before the anisotropy of the cosmic microwave background was discovered).<br /><br />And after all this, general relativity survives and most of the other theories really don't. Theories with additional vector and tensor couplings are right out, and scalar-tensor theories looked very doubtful. This is astounding because general relativity, with no free parameters, is the most restrictive theory of the bunch, the one with the least wiggle room to respond to those occasional experiments that are likely to tell the poor theoretician that his baby isn't as beautiful as he thought. In a Popperian world, this makes Einstein's theory the strongest or the survivors, and makes the scalar-tensor theories look bad -- especially when some theorist says that it's all this doom and gloom experiment stuff is okay, because you can always play with the parameters of his theory so that it will work (as one did in one of the papers Randy and I are reading for next week's recording -- it will probably be out around March). These experiments are very effective to be able to eliminate so many different kinds of theories, and with the exception of general relativity, those that survive only survive by being slippery.<br /><br />And that was what everything looked like in 1993. If you look at Will's 2014 update, general relativity looks even better. [edit - I just noticed a <a href="https://amzn.to/2YrkBTK" target="_blank">new edition</a> is coming out at the end of 2018; if it's 2019 or later and you read this, could you <a mailto://physicsfm.rantschler@gmail.com>e-mail me</a> so I can update the links?]<br /><br />Again, this is a wonderful book. We were going to use this, after Quantum Paradoxes, for the second book on PhysicsFM when we were doing that, and for good reason. It is little on the technical side, but if you've gotten through an undergraduate course in gravitation you should be okay (although there are a few chapters in the middle you might feel a little bit over your head in), and I recommend it heartily.<br /><br />I need to find a better way to sign off. I still sound like a recommendation letter.<br /><br />I really hope this book gets that internship.<br><br> * Links are to Amazon pages. If you buy from them, they'll give Physics Frontiers a cut.<br><br> [Edit 5/2/2020 - Removed discussion of new edition, since it's been out for two years, and added new links to Amazon, because they kicked me out of the associates program for underperformance, again, probably in 2018.]PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-23880523061121529112017-09-17T07:18:00.001-07:002020-07-07T19:08:47.368-07:00Physics Frontiers Index<a href = http://frontier.physicsfm.com/>Podcast Home</a><br><br><u>Posted Shows:</u><br /><u></u><br />1. <a href="http://physicsfm-frontiers.blogspot.com/2016/10/g4v-gravitational-4-vector-formulation.html">G4V: The Gravitational 4-Vector Formulation of Gravity</a><br> (Recorded: 10/8/2016) (Published: 10/31/2017) <a href="https://youtu.be/tuJMdhviObI" target="_blank">[video]</a><br />2. <a href="http://physicsfm-frontiers.blogspot.com/2016/11/the-de-broglie-bohm-pilot-wave.html">The de Broglie-Bohm Interpretation of Quantum Mechanics</a><br> (Recorded: 10/15/2016) (Published: 11/15/2017) <a href="https://youtu.be/Y0PBlvfrVbE" target="_blank">[video]</a><br />3. <a href="http://physicsfm-frontiers.blogspot.com/2016/12/gravitoelectromagnetism.html">Graviteoelectromagnetism</a><br> (Recorded: 10/22/2016) (Published: 12/6/2017) <a href="https://youtu.be/I8Iw8HfjMNk" target="_blank">[video]</a><br />4. <a href="http://physicsfm-frontiers.blogspot.com/2017/01/phononics.html">Phononics</a><br> (Recorded: 11/5/2016) (Published: 1/4/2017)<br />5. <a href="http://physicsfm-frontiers.blogspot.com/2017/01/pilot-wave-hydrodynamics.html">Pilot Wave Hydrodynamics</a> <br>(Recorded: 11/20/2016) (Published: 1/20/2017)<br />6. <a href="http://physicsfm-frontiers.blogspot.com/2017/02/randy-shares-couple-of-his-favorite.html">General Relativity for the Experimentalist</a> <br>(Recorded: 11/26/2016) (Published: 2/14/2017) <br />7. <a href="http://physicsfm-frontiers.blogspot.com/2017/03/virtual-graviational-dipoles.html">Virtual Gravitational Dipoles</a> <br>(Recorded: 12/3/2016) (Published: 3/14/2017)<br />8. <a href="http://physicsfm-frontiers.blogspot.com/2017/05/vacuum-fluctuations-and-casimir-effect.html">Vacuum Fluctuations and the Casimir Effect</a><br> (Recorded: 12/10/2016) (Published: 4/27/2017)<br />9. <a href="http://physicsfm-frontiers.blogspot.com/2017/06/fr-theories-of-gravity.html">f(R) Theories of Gravity</a><br> (Recorded: 12/17/2016) (Published: 6/2/2017)<br />10. <a href="http://physicsfm-frontiers.blogspot.com/2017/06/requirements-for-gravitational-theories.html">Requirements for Gravitational Theories</a><br> (Recorded: 1/15/2017) (Published: 6/30/2017)<br />11. <a href="http://physicsfm-frontiers.blogspot.com/2017/07/photonic-molecules-and-optical-circuits.html">Photonic Molecules and Optical Circuits</a> <br>(Recorded: 1/21/2017) (Published: 7/16/2017)<br />12. <a href="http://physicsfm-frontiers.blogspot.com/2017/08/a-graviational-arrow-of-time.html">A Gravitational Arrow of Time</a> <br>(Recorded: 1/28/2017) (Published: 8/20/2017)<br />13. <a href="http://physicsfm-frontiers.blogspot.com/2017/09/exotic-looped-trajectories-in-quantum.html">Exotic Photon Trajectories in Quantum Mechanics</a> <br>(Recorded: 2/4/2017) (Published: 9/14/2017)<br />14. <a href="http://physicsfm-frontiers.blogspot.com/2017/10/stochastic-electrodynamics.html">Stochastic Electrodynamics</a><br> (Recorded: 2/11/2017) (Published: 10/4/2017)<br />15. <a href="http://physicsfm-frontiers.blogspot.com/2017/10/five-proven-methods-of-levitation.html" target="_blank">Five Proven Methods of Levitation</a><br> (Recorded: 3/5/2017) (Published: 10/21/2017)<br />16. <a href="http://physicsfm-frontiers.blogspot.com/2017/11/stochastic-resonance-energy-harvesting.html" target="_blank">Stochastic Resonance Energy Harvesting</a><br> (Recorded: 3/11/2017) (Published: 11/6/2017) <br />17. <a href="http://physicsfm-frontiers.blogspot.com/2017/11/the-physics-of-time-travel.html" target="_blank">The Physics of Time Travel</a> <br> (Recorded: 4/2/2017) (Published: 11/23/2017) <br />18. <a href="http://physicsfm-frontiers.blogspot.com/2017/12/the-2t-physics-of-itzhak-bars.html">The 2T Physics of Itzhak Bars</a><br> (Recorded: 4/8/2017) (Published: 12/6/2017)<br /><strike>19. Exoplanets. </strike> [Lost track]<br>(Recorded: 4/15/2017)<br />20. <a href="http://physicsfm-frontiers.blogspot.com/2017/12/time-crystals.html">Time Crystals</a> <br>(Recorded: 4/22/2017) (Published: 12/21/2017)<br />21. <a href="http://physicsfm-frontiers.blogspot.com/2018/01/the-origin-of-inertia.html">The Origin of Inertia</a> <br> (Recorded: 4/29/2017) (Published: 1/10/2018)<br />22. <a href="http://physicsfm-frontiers.blogspot.com/2018/01/weyl-and-quasiparticles.html">Weyl Quasiparticles</a><br> (Recorded: 5/7/2017) (Published: 1/18/2018)<br>23. <a href = http://physicsfm-frontiers.blogspot.com/2018/02/dark-energy.html>Dark Energy</a><br> (Recorded: 5/20/2017) (Published: 2/8/2018)<br />24. <a href = http://physicsfm-frontiers.blogspot.com/2018/02/the-island-of-stability.html>The Island of Stability</a><br> (Recorded: 5/27/2017) (Published: 2/23/2018)<br />25. <a href = http://physicsfm-frontiers.blogspot.com/2018/03/gravitational-field-propulsion.html>Gravitational Field Propulsion</a><br> (Recorded: 6/11/2017) (Published: 3/15/2018)<br />26. <a href = http://physicsfm-frontiers.blogspot.com/2018/03/antimatter-production-at-potential.html>Antimatter Production at a Potential Boundary</a><br> (Recorded: 6/17/2017) (Published: 3/25/2018)<br />27. <a href = http://physicsfm-frontiers.blogspot.com/2018/04/the-gravitational-equivalence-principles.html>The Gravitational Equivalence Principles</a><br> (Recorded: 9/10/2017) (Published: 4/14/2018)<br />28. <a href = http://physicsfm-frontiers.blogspot.com/2018/04/the-quantum-vacuum-and-casimir-effect.html> The Quantum Vacuum and the Casimir Effect </a><br> (Recorded: 9/16/2017) (Published: 4/24/2018)<br />29. <a href = http://physicsfm-frontiers.blogspot.com/2018/05/gravitational-alternatives-to-dark.html> Gravitational Alternatives to Dark Energy </a> <br> (Recorded: 10/15/2017) (Published: 5/14/2018)<br />30. <a href = http://physicsfm-frontiers.blogspot.com/2018/05/the-consistent-histories-interpretation.html>Consistent Histories Interpretation of Quantum Mechanics</a><br> (Recorded: 10/29/2017) (Pubished: 5/24/2018)<br>31. <a href = http://physicsfm-frontiers.blogspot.com/2018/06/the-parameterized-post-newtonian.html>The Parameterized Post-Newtonian Framework</a><br> (Recorded: 11/12/2017) (Published: 6/8/2018) <br />32. <a href = http://physicsfm-frontiers.blogspot.com/2018/07/tunneling-time.html>Tunneling Time</a> <br> (Recorded: 11/25/2017) (Published: 7/6/2018) <br />33. <a href = http://physicsfm-frontiers.blogspot.com/2018/07/retrocausality.html>Retrocausality</a><br> (Recorded: 3/3/2018) (Published: 7/25/2018)<br>34. <a href = https://physicsfm-frontiers.blogspot.com/2018/08/cpt-symmetry-and-gravitation.html >CPT Symmetry and Gravitation</a><br> (Recorded: 3/28/2018) (Published: 8/10/2018)<br>35. <a href = http://physicsfm-frontiers.blogspot.com/2018/09/the-string-theory-landscape.html>The String Theory Landscape</a><br>(Recorded: 5/12/2018) (Published: 9/21/2018)<br>36. <a href = http://physicsfm-frontiers.blogspot.com/2018/10/metamaterial-stress-tensor.html>The Electromagnetic Stress Tensor in Metamaterials</a> <br>(Recorded: 5/26/2018) (Published: 10/14/2018)<br>37. <a href = https://physicsfm-frontiers.blogspot.com/2018/10/the-einstein-cartan-torsion-field-theory.html>The Einstein-Cartan Theory Torsion Field Theory</a> <br>(Recorded: 6/10/2018) (Published: 10/29/2018)<br>38. <a href = https://physicsfm-frontiers.blogspot.com/2018/11/the-dimensionality-of-space-time.html>Why is Space-Time Four Dimensional?</a><br>(Recorded: 9/8/2018) (Published: 11/25/2018)<br>39. <a href = https://physicsfm-frontiers.blogspot.com/2018/12/negative-effective-mass.html>Negative Effective Mass</a><br>(Recorded: 9/29/2018) (Published: 12/9/2018)<br>40. <a href = https://physicsfm-frontiers.blogspot.com/2018/12/the-octonions.html>The Octonions</a> <br>(Recorded: 10/20/2018) (Published: 12/23/2018)<br>41. <a href = https://physicsfm-frontiers.blogspot.com/2019/02/the-chameleon-field.html>The Chameleon Field</a> <br>(Recorded: 11/3/2018) (Published: 2/24/2019)<br>42. <a href = https://physicsfm-frontiers.blogspot.com/2019/05/entropic-gravity.html>Entropic Gravity</a> <br>(Recorded: 4/4/2019) (Published: 5/3/2019)<br>43. <a href = https://physicsfm-frontiers.blogspot.com/2019/06/the-positive-energy-theorem.html>The Positive Energy Theorem </a> <br>(Recorded: 12/9/2017) (Published: 6/6/2019)<br>44. <a href = https://physicsfm-frontiers.blogspot.com/2019/07/spooky-action-at-distance.html>Spooky Action at a Distance</a> <br>(Recorded: 5/2/2019) (Published: 7/15/2019)<br>45. <a href = https://physicsfm-frontiers.blogspot.com/2019/08/loop-quantum-gravity.html>Loop Quantum Gravity</a> <br>(Recorded: 6/13/2019) (Published: 8/16/2019)<br>46. <a href = https://physicsfm-frontiers.blogspot.com/2019/09/wigners-friend.html>Wigner's Friend</a> <br>(Recorded: 7/18/2019) (Published: 9/21/2019)<br>47. <a href = https://physicsfm-frontiers.blogspot.com/2019/11/sabine-hossenfelders-bimetric-theory-of.html>Bimetric Gravity</a><br>(Recorded: 8/15/2019) (Published: 11/23/2019)<br> 48. <a href = https://physicsfm-frontiers.blogspot.com/2020/01/the-gertsenshtein-effect.html>Graviton-Photon Oscillations</a><br>(Recorded: 9/13/2019) (Published: 1/19/2020)<br>49. <a href = https://physicsfm-frontiers.blogspot.com/2020/04/the-unruh-effect.html> The Unruh Effect</a><br>(Recorded: 10/31/2019) (Published: 4/4/2020)<br>50. <a href = https://physicsfm-frontiers.blogspot.com/2020/05/x17.html> X17</a><br>(Recorded: 12/6/2019) (Published:5/3/2020)<br>51. <a href = https://physicsfm-frontiers.blogspot.com/2020/06/gravitational-wave-astronomy.html>Gravitational Wave Astronomy</a><br>(Recorded: 3/19/2020) (Published:6/9/2020)<br>52. <a href = https://physicsfm-frontiers.blogspot.com/2020/07/sterile-neutrinos.html>Sterile Neutrinos</a><br>(Recorded: 4/24/2020) (Published:7/7/2020)<br><br><u>Coming Soon (in editing)</u>:<br /><br> 53. Electromagnetic-Gravitational Repulsion<br><br><u>Upcoming Shows (recorded and unedited)</u>:<br /><br /> 54. The ANITA Experiment<br>55. Multiversality<br> <br /><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br /><u>Next Recording</u>:<br /><br> 56. The Anomalous Magnetic Moment of the Muon <br><br><br><br><a href = http://frontier.physicsfm.com/>Podcast Home</a> PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com1tag:blogger.com,1999:blog-6472333724958467896.post-21499929476617553462017-09-06T07:16:00.001-07:002019-07-24T08:50:58.875-07:00Suggested Shows for Physics FrontiersThis post is a list of topics Randy and I have discussed, and is intended to be kept up to date in what should be an easily found spot so that I don't lose any more lists of possible show topics.<br /><br />Please feel free to comment about topics you'd like to see discussed, especially if you have a reference for them. Priority goes to references in refereed publications.<br /><br />Also please feel free to suggest ways to narrow down or split the topics; many of these are too broad, especially when following a show format focuses on discussing one or two scientific papers.<br /><br />Before suggesting a topic, make sure that we haven't already discussed it in the <a href="http://physicsfm-master.blogspot.com/2017/09/physics-frontiers-index.html">index</a>. But, if there's something from the show that you'd like to hear more about, we're also willing to revisit topics, similar topics, and aspects of topics. <br /><br /><b><u>Possible topics:</u></b><br /><div><u><b></b><br /></u></div><div><b>Gravitation</b></div><div><b><br /></b></div><div>Ghosts <a href="https://arxiv.org/abs/hep-ph/0311312" target="_blank">1</a></div><div>Galileon <a href="https://arxiv.org/abs/0811.2197" target="_blank">1</a></div><div>de Sitter Unvierse<br />Chameleon Fields <a href="https://arxiv.org/abs/astro-ph/0309300" target="_blank">1</a><u> <a href="https://arxiv.org/abs/gr-qc/9810026" target="_blank">2</a></u><br />Bimetric Theories of Gravity<br />The Parameterized Post-Newtonian Framework<br />Post-Post-Newtonian Physics<br />Black Holes and Hawking Radiation<br />Mass, Gravitational Binding Energy, and Nuclear Mass Defect<br />massive gravity <a href="https://arxiv.org/abs/1401.4173" target="_blank">1</a><br />Cosmological Constant <a href="https://arxiv.org/abs/1205.3365" target="_blank">1</a><br />Gravitational Waves<br />More Experimental Evidence in Gravitation – Hafele Keating Exp., Precession of Perihelion of Mercury, Deflection of Starlight, time dilation, gravitational waves, frame dragging, etc (don't think we did enough on this one; some topics need more elaboration) Tests of Lorentz Invariance <a href="https://arxiv.org/abs/1304.5795" target="_blank">1</a><u> <a href="https://arxiv.org/abs/gr-qc/0502097" target="_blank">2</a></u><br /><div class="yiv5508091176MsoNormal" id="yui_3_16_0_ym19_1_1505152506168_2240" style="-webkit-text-stroke-width: 0px; background-color: white; display: block; font-style: normal; font-weight: normal; letter-spacing: normal; margin: 0px; orphans: 2; padding: 0px; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px;"><span id="yui_3_16_0_ym19_1_1505152506168_2250"><span style="color: black; font-family: inherit;">Gravity Probe B and Gravitomagnetism <a href="https://physics.aps.org/articles/v4/43" target="_blank">1</a><u> </u></span></span><br /><span style="color: black; font-family: inherit;">Dark Energy Survey results <a href="https://arxiv.org/abs/1708.01530" target="_blank">1</a></span><br />Unruh's Law<br />Bekenstein's Law<br />Bekenstein's Bound<br />Dark Matter <a href="https://arxiv.org/abs/1701.01840" target="_blank">1</a><br />Inhomogeneous Cosmology <a href="https://arxiv.org/abs/1612.08222" target="_blank">1</a><br />k-moufage <a href="https://arxiv.org/abs/1509.00611" target="_blank">1</a> <a href="https://arxiv.org/abs/0905.2943" target="_blank">2</a><br /><span style="background-color: transparent; color: black; display: inline; float: none; font-family: "times new roman"; font-size: 16px; font-style: normal; font-variant: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-decoration: none; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px;">Unruh Effect</span><br /><u></u><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br /></div><b></b></div><div><b><i><u><sub><sup><strike><br /></strike></sup></sub></u></i></b></div><div><b>Quantum Mechanics</b></div><div><b></b><br /></div><div>Consistent Histories Interpretation (Griffiths, Omnes)<br />Multiple Worlds <a href="https://arxiv.org/abs/1604.07422" target="_blank">1</a></div><div>Process Quantum Theory (David Finkelstein)</div><div>Nonlinear Schrodinger Equations and Wavefunction Collapse (still a thing?)<br /><b></b></div><div>Rosenfeld Universe</div><div>Wheeler-Feynman Absorber Theory<br />Higgs Stuff<br /><div class="yiv5508091176MsoNoSpacing" id="yui_3_16_0_ym19_1_1505152506168_2242" style="-webkit-text-stroke-width: 0px; background-color: white; display: block; font-style: normal; font-weight: normal; letter-spacing: normal; margin: 0px; orphans: 2; padding: 0px; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px;"><span id="yui_3_16_0_ym19_1_1505152506168_2241"><span style="color: black; font-family: inherit;">Wigner function and Weyl transforms – transition from QM to classical</span></span><br />Double slit experiments with superconductors<br />Standard Model: What's Next? <a href="https://arxiv.org/abs/1704.02821">1</a> (The squarkless gluiNO)<br />Stochastic Electrodynamics (time and quanta and GR) <a href="https://arxiv.org/pdf/1409.3131.pdf" target="_blank">1</a> <a href="https://arxiv.org/pdf/1205.0916.pdf" target="_blank">2</a> <a href="http://iopscience.iop.org/article/10.1088/1742-6596/701/1/012023/pdf" target="_blank">3</a><br />Asymptotic Freedom<br />Quantum Gravity Oscillations<br /><br /><b></b></div></div><div><b><i><u><sub><sup><br /></sup></sub></u></i></b></div><div><b>Vacuum</b></div><div><b><br /></b></div><div>Mass for the Graviton <a href="https://arxiv.org/abs/gr-qc/9705051" target="_blank">1</a></div><div>Space-Time Vacuum (specific theories? which?)</div><div>Twistors ala Penrose <a href="http://aip.scitation.org/doi/abs/10.1063/1.1705200" target="_blank">1</a><u> <a href="https://arxiv.org/abs/1704.07464" target="_blank">2</a></u><br />Superstring/Brane stuff (More specific?)<br />Non-commutative Geometry [Alain Connes] <a href="https://arxiv.org/abs/hep-th/0608226" target="_blank">1</a><u> <a href="https://arxiv.org/abs/1411.0977" target="_blank">2</a></u><br />Loop Quantum Gravity <a href="https://arxiv.org/abs/gr-qc/9710008" target="_blank">1</a> <a href="https://arxiv.org/abs/1012.4707" target="_blank">2</a><br />Links between Loop Quantum Gravity and String Theory <a href="https://arxiv.org/abs/hep-th/9903166" target="_blank">1</a><br />Spin Networks <a href="https://arxiv.org/abs/hep-th/9801022" target="_blank">1</a><br />Holographic Principle <a href="https://arxiv.org/abs/1608.02932" target="_blank">1 </a><a href="https://arxiv.org/abs/hep-th/9409089" target="_blank">2</a> <br />Emergent Gravity (verlinde) <a href="https://arxiv.org/abs/1611.02269" target="_blank">1</a><br />Qubits in Space <a href="https://arxiv.org/abs/1702.06959" target="_blank">1</a><br />Consistent Histories and Relativity (Topos) (Christopher Isham) <a href="https://arxiv.org/abs/quant-ph/0703060" target="_blank">1</a> <a href="https://arxiv.org/abs/quant-ph/0703062" target="_blank">2</a> <a href="https://arxiv.org/abs/quant-ph/0703064" target="_blank">3</a> <a href="https://arxiv.org/abs/quant-ph/0703066" target="_blank">4</a><br /><br /><br /><b></b><br /><b>Materials Physics</b><br /><b></b><br />Bose-Einstein Condensation of Quasi-Particles<br />Massless Dirac Fermions (on the verge of exciton condensation)<br />Excitons in general.<br />Metamaterials (too broad)<br /><b></b></div><div>Spin States in Quantum Fluid Analogy (analogy to what?)</div><div>Sonoluminescence and Sonofusion<br />Fusion Power<br />Superparamagentism<br />Thermionic Energy Harvesting<br /><br /><b></b></div><div><b><i><u><sub><sup><br /></sup></sub></u></i></b></div><div><b>Uncategorized</b></div><b></b><br />Buesard-Poliwell Reactor (wuzzis?)<br /><span style="background-color: white; color: black; display: inline; float: none; font-family: "helvetica neue" , "arial" , "helvetica" , sans-serif; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px;"><br /></span> <span style="background-color: white; color: black; display: inline; float: none; font-family: "helvetica neue" , "arial" , "helvetica" , sans-serif; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px;">From Podomatic Comment: Paul Corkum did a lecture entitled " a molecule takes a selfie". This was a lecture discussing his work with attosecond lasers. I'm not sure if you're familiar with this topic. It was fascinating in many respects. One being a new way of creating quantum computers. He only touched on that possibility during the lecture. </span><br /><span style="background-color: white; font-family: "arial";"><br /></span><span style="background-color: white; font-family: "arial";"></span><br /><span style="background-color: white; font-family: "arial";"><br /></span><span style="background-color: white; font-family: "arial";">People to Investigate:</span><br />Raphael Sorkin<br /><br><br>Linder:<br><ul><li><a href = https://arxiv.org/abs/1608.01531> Matters of time directionality in gravitation theory </a></li><li><a href = https://arxiv.org/abs/gr-qc/0603005> Theoretical basis for a solution to the cosmic coincidence problem </a></li></ul><br><br>Hossenfelder:<BR><BR><UL><li><A HREF = https://arxiv.org/ABS/0911.2761>Phenomenological Quantum Gravity</a><br><li><a href = https://arxiv.org/abs/hep-ph/0410122>The Minimal Length and Large Extra Dimensions</a><br><li><a href = https://arxiv.org/abs/hep-ph/0405127>Running Coupling with Minimal Length</a><br></ul> <span style="background-color: white; font-family: "arial";"><br /><b></b><span style="background-color: white; color: black; display: inline; float: none; font-family: "helvetica neue" , "arial" , "helvetica" , sans-serif; font-size: 12px; font-style: normal; font-weight: normal; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px;"><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><span style="font-size: small;"></span><span style="font-family: "arial" , "helvetica" , sans-serif;"></span><span style="font-family: "courier new" , "courier" , monospace;"></span><span style="font-family: "georgia" , "times new roman" , serif;"></span><span style="color: black;"></span><span style="font-family: inherit;"></span>[Last Updated 7/24/2019]</span></span><br /><b><i></i><u></u><sub></sub><sup></sup><strike></strike><br /></b><br /><u><a href="http://physicsfm-master.blogspot.com/2017/09/physics-frontiers-index.html">Posted Shows</a></u>PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com8tag:blogger.com,1999:blog-6472333724958467896.post-59127903101319517002017-09-04T09:59:00.003-07:002019-07-15T18:22:34.423-07:00Speakable and Unspeakable in Quantum Mechanics by J.S. BellJohn S Bell is well known because of his development of what is known as Bell’s theorem – a proof showing that quantum entanglement means that local causality does not exist. This book, <i>S<a href="https://amzn.to/2lBTOmo" target="_blank">peakable and Unspeakable in Quantum Mechanics</a></i>, is a collection of 24 technical and semi-technical papers written by Bell on that topic. Bell’s outlook is partially physical and partially philosophical, making these papers quite interesting reading. At this point I would say it’s incredibly well-written and accessible, but I remember trying to read this as an undergraduate in the 90’s (when there were only 22 papers; I picked this one up because I lost the old one in a postdoc-postdoc transition) and having quite a lot of trouble with it. Many of the papers seem to be addressed to philosophers, whereas others are standard physics papers. But most of them lay in the no man’s land between theoretical physics and the philosophy of science.<br /><br /><a href="https://www.amazon.com/Speakable-Unspeakable-Quantum-Mechanics-Philosophy/dp/0521523389/ref=as_li_ss_il?crid=13WGBJTSPJWXD&keywords=speakable+and+unspeakable+in+quantum+mechanics&qid=1563239763&s=gateway&sprefix=speakable+an,aps,226&sr=8-1&linkCode=li2&tag=physicsfm0e-20&linkId=e9945dd72cdab20273ac5df290a40eb6&language=en_US" target="_blank"><img border="0" align="right" src="//ws-na.amazon-adsystem.com/widgets/q?_encoding=UTF8&ASIN=0521523389&Format=_SL160_&ID=AsinImage&MarketPlace=US&ServiceVersion=20070822&WS=1&tag=physicsfm0e-20&language=en_US" ></a><img src="https://ir-na.amazon-adsystem.com/e/ir?t=physicsfm0e-20&language=en_US&l=li2&o=1&a=0521523389" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" />Many of Bell’s concerns run throughout the book, with slight variations from paper to paper. One of them is the incoherence of quantum mechanics: <br /><br /><blockquote class="tr_bq">So long as wave packet reduction is an essential component [of quantum mechanics], so long as we don’t know exactly how and when it takes over for the Schrödinger equation, we do not have an exact and unambiguous formulation of our most fundamental theory.</blockquote>And that cannot stand. In order to have a reasonably scientific quantum theory, you should be able to express exactly when the wavefunction collapses. This is for several reasons, but what Bell really wants to know is this: if I measure the magnetic moment of an electron in a magnetic field, when does the electron decide which <i><span style="font-family: "courier new" , "courier" , monospace;">Sz</span></i> state it is in (up or down)? Here are some options, which aren’t all of them:<br /><br /><ul><li>Does it do so when I turn on the static magnetic field?</li><li> Does it do so when the microwave detection field reaches it? </li><li>Does it do so when the response is felt by the field? </li><li>Does it do so when the inductive current is generated in the pick-up coil? </li><li>Does it do so when the microwave current passes through the diode detector?</li><li>Does it do so when the detector is read by the multimeter? </li><li>Does it do so after the multimeter output is analyzed by the computer? </li><li>Does it do so when the analysis is displayed on the screen? </li><li>Does it do so when the graduate student save the data? </li><li>Does it do so when the Ph.D. looks at the charts?</li><li> Does it do so when the paper is submitted or accepted? </li><li>Does it do so when the paper is printed or earns an award? </li></ul><div>The Ph.D. gag was Bell’s favorite sarcastic line in these papers (judging by the number of re-uses), which were drawn from publications like <i>Reviews of Modern Physics</i>, <i>Foundations of Physics</i>, and so on, as well as invited lectures and symposia and book chapters. The important thing is that “measurement,” resulting in the collapse of the wavefunction, is an essential part of quantum theory, but it is not well defined theoretically. In Bell’s words:</div><div><blockquote class="tr_bq">The Landau-Lifshitz formulation…when applied with good taste and discretion is adequate for all practical purposes,” but it is “still ambiguous in principle about exactly when and exactly how the collapse occurs…” </blockquote> This is the same problem that led Schrödinger to torture analogical cats late at night in obscure journals.* Furthermore, Bell feels that “highly idealized ‘measurements’ should be replaced by an interaction of continuous, if variable, character.” This is essentially the thing that Aharonov explores in the book that started PhysicsFM off, <i>Quantum Paradoxes</i>. </div><div><br /></div><div>Bell returns again and again to the Einstein-Poldosky-Rosen paradox (EPR, in case I use it again), its reformulation by Bohm into a more physical experiment, and finally, the Aspect Experiment which was the first practical test of the EPR paradox (the introduction to the new edition was written by Alain Aspect himself). The Aspect Experiment really turned Bell’s Theorem into an experiment, but Bell’s theorem was one that elucidated the true importance of what had been an almost forgotten result by Bohm – for the practical reason that no one could figure out how to do the experiment with 1950’s technology. The experiment took entangled photons (rather than electrons in Bohm’s experiment) and looked at their correlations. If you are looking at just up vs. down, clockwise vs. counterclockwise, and so on, then the correlations are fairly simple and come directly from conservation laws. However, when you tilt the detectors with respect to each other, the classical and quantum predictions diverge in such a way that an inspired and talented experimental physicist can tickle out the subtle differences. And when he did that experiment, Alain Aspect fount that quantum mechanics won and Bell’s theorem implied that local causality** was lost. </div><div><br /></div><div>And at that point, “the concept of ‘reality’ [became] an embarrassing one for many physicists,” according to Bell. </div><div><br /></div><div>Much of the book also discusses the interpretation of quantum mechanics. Bell looks at interpretations differently than most. In “Six Possible Worlds of Quantum Mechanics,” Bell categorizes theories into a 3 x 2 matrix. Bell’s three main categories are a no-nonsense measurement-based approach that doesn’t attempt to understand what is happening between measurements, that the wavefunction collapse is a real thing that happens to the quantum system and changes it, and that there are two or more subsystems in any quantum system that account for wave-particle duality (hidden variables). The “x2” breaks three interpretation into unromantic and romantic pairs. The romantic dual makes the interpretation interesting without adding any true meaning. </div><div><br /></div><div>Thus, you have this practical approach being paired with the Bohrian Copenhagen interpretation where the universe holds complimentary views, macroscopic and microscopic, simultaneously. The collapse interpretation is paired with a Wignerian dualistic interpretation where it is the act of intelligent observation that collapses the wave function. The de Broglie-Bohm hidden variable interpretation is paired with Everett’s multiversal interpretation where each possible way in which something can happen does happen – just in another universe. </div><div><br /></div><div>This is a very different view of Everett. Specifically, Bell’s interpretation of the many-worlds interpretation is to say that the many-worlds part is inessential. It is comforting, he says, to cosmologists (because it allows them to ignore the collapse of the universal wavefunction), but the additional “worlds” don’t add any new physics or understanding of what is happening. So, he says, if you strip the romantic multiverse from Everett, you have a (possibly different) nonlinear hidden variable theory than conjured by Bohm. I’ve never seen anyone else say that. To everyone else the many-worlds of the many-worlds interpretation are the point. </div><div><br /></div><div>The most annoying gripe Bell makes is to continually harp on his theory of “Be-ables,” which would be a subset of quantum mechanical observables with certain properties that make things less weird. I don’t think it helps so much as he thinks, and it certainly wasn’t clear what the different was, other than terminology, the in the first half-dozen papers he mentioned them in. </div><div><br /></div><div>In sum, I very much like this book. It is wonderfully written, physically insightful, and historically important. Many of the points, especially those from lectures, are very much Bell’s own thoughts and just his own thoughts that no one else thinks (beables), but even there he is trying to make points about the unsuitability of quantum theory without refinements that tell us what several of these mathematical objects that we use refer to in the physical world.</div><div><br /></div><div>* Well, not really obscure. But still. </div><div>** “Local causality” might seem to be a strange combination of words, but it is what we normally think of as causality. First, if P causes Q, then P occurs before Q. Second, if P causes Q, it should be close enough to affect Q by special relativity. That is P is close enough to Q that light can travel from P to Q. It really is what you’d think about as causality in relativity theory. </div>PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-64207320590220923042017-08-05T11:49:00.000-07:002018-02-09T13:19:58.654-08:00Quantum Mechanics and the Particles of Nature by Anthony Sudbery<iframe style="width:120px;height:240px;" align = "right" marginwidth="0" marginheight="0" scrolling="no" frameborder="0" src="//ws-na.amazon-adsystem.com/widgets/q?ServiceVersion=20070822&OneJS=1&Operation=GetAdHtml&MarketPlace=US&source=ss&ref=as_ss_li_til&ad_type=product_link&tracking_id=physicsfm-20&marketplace=amazon®ion=US&placement=0521277655&asins=0521277655&linkId=1ca74c1d0f11728c6c34fef287a13bae&show_border=true&link_opens_in_new_window=true"></iframe><I>Quantum Mechanics and the Particles of Nature: an outline for mathematicians</I> by Anthony Sudbery has been one of my favorite books on quantum mechanics since I was an undergraduate. This is despite the fact that I probably haven't read it from cover-to-cover ever in my life. It has, however, been a book that I have returned to again and again when looking at quantum mechanics.<br><br> The book is a curious amalgam of physics and mathematics. The meat of the book, chapters 2-4, 6 and 7, are formally sound, mathematical beasts proceeding axiomatically though their various topics and become highly algebraic, in the modern sense. Chapter 3, on "Quantum Dynamics" introduces Lie algebras and symmetry groups (SU(2) and all that), and Sudbery never looks back. Most of the book proceeds with a pattern of: (1) description of the physics, (2) a theorem that encapsulates the description, and (3) a rigorous proof of the theorem. This is incredibly abstract for an introduction to the subject -- unless you're an undergraduate mathematics student, which this work was designed for. Sudbery is not trying to teach solution techniques, but rather to express how the artifice of quantum mechanics fits together logically, and this is often as much the province of applied mathematics as it is theoretical physics. I don't know the demarcation between the two, you'll have to get an applied mathematician and a theoretical physicist that are working on similar subjects to draw the line for you.<br><br>[It is designed for the British student, not the American one. I went through many undergraduate textbooks from England that I found extraordinarily good that were far too dense for any of my students. This of course may not be true for all colleges, but it was my experience.]<br><br>I have a few advantages over the usual reader for a book like this: (1) I survived my graduate Quantum Mechanics courses, (2) I have a degree in "theoretical mathematics" (as opposed to applied mathematics), so I am familiar with proofs and the axiomatic style and have even taken a modern algebra course, (3) I have taught both 300-level modern physics, materials science, and nanotechnology courses to undergraduates, all of which include a reasonable amount of quantum mechanics (even if very basic), and of course, (4) I talk about these sorts of things on a podcast. SO the going this time was easy, even if it is a book that I've owned for twenty-five years.<br><br> I originally found this book in the college bookstore -- we had an extraordinary college bookstore when I was an undergrad -- and immediately fell in love with it upon reading the first chapter. I'm sure I got through the next two and the fifth, but I don't know how much of the others. The first chapter, "Particle and Forces" is as lucid a description of particle physics as I've ever read, and it's a description that stayed with me even after I forgot where it came from. I found it so clear and memorable that I thought it came from a popular book, and when in the 2000s I was looking for it, I kept looking in old Scientific American books (<I>Particles and Forces: at the heart of the matter</I>, it think it was; it seems to have disappeared) and Polkinghorne's <I>The Quantum World</I> (which hasn't disappeared, and I'd replace if it did) and similar books that I'd read a little bit earlier or later. I did not go back to a textbook that I was working in my spare time and didn't actually finish. The reason why I wanted to find it again is that I'd attempted this book before I took a quantum mechanics course, and it left a lasting impression on how I thought about the subject. I finally found out that this was the book I had been looking for, off and on, for ten years when I pulled it out to help me prepare lectures for modern physics when I taught it.<br><br> But the thing that brought me back to this book most of all was chapter 5, "Quantum Metaphysics." This talks about the <a href = http://paradoxes-physicsfm.blogspot.com/2015/04/quantum-measurements.html>quantum theory of measurement</a>, <a href = http://physicsfm-frontiers.blogspot.com/2016/11/the-de-broglie-bohm-pilot-wave.html> The de Broglie-Bohm Interpretation of Quantum Mechanics</a> and <a href = http://paradoxes-physicsfm.blogspot.com/2017/03/quantum-metaphysics.html> Quantum Interpretations</a> in a rigorous way. Even as an undergraduate, I found this chapter entrancing. When I took a philosophy course on (philosophical) cosmology, I used this general approach to discuss how the various interpretations of probability relate to the interpretations of quantum mechanics (which not think is a lot harder than I thought it was then). You can get an idea about how clear this chapter is if you listen to Randy and I talk about section 5.5 as the intermission in our discussion of Aharanov and Rohrlich's <I>Quantum Paradoxes</I>. It is a touchstone that I come back to every time I think about how to think about quantum mechanics.<br><br> That said, I had some rough going with the problems in this book. One reason is that so many of them are proofs, and a problem I've always had with proofs is determining whether or not I've really justified every step. Too often I worry that this or that step is for a special case and isn't extensible to other cases, and so on -- and I'm not as lucky as a student because I don't have a red pen man to tell me what I did wrong or reassure me that I did it right (students may disagree about the desirability of the red pen men). Another is that I think Sudbery expects you to have actually learned things in a mathematics course, meaning that I have to reconstruct the methods for the more application-oriented problems. This makes the problems especially valuable, and I find myself writing up multi-page analyses of what I did to solve a problem to remind myself what I did -- something I haven't done since my graduate work. <br><br> The chapters in between these two, 2-4, dealing with "Quantum Statics", "Quantum Dynamics", and "Some Quantum Systems" are all equally rewarding, giving a mathematical picture of the basic ideas of quantum mechanics. The last two chapters are more difficult. "Quantum Numbers" and "Quantum Field Theory" go a little beyond what is presented in most undergraduate courses. They talk about isospin and hypercharge, the weak and strong forces, and grand unification. All very interesting stuff that satisfy the "particles of nature" part of the title more than the "quantum mechanics. The integration of abstract algebra, matrix mechanics, and differential equations is complete here, and if you let your guard down reading about quantum metaphysics, it will bit you in the ass. It did me. I had a harder time with these two chapters than Cohen's <I>An Introduction to Hilbert Space and Quantum Logic</I> (available at <a href = https://www.walmart.com/ip/An-Introduction-to-Hilbert-Space-and-Quantum-Logic/21306294?wmlspartner=wmtlabs&adid=22222222222043777771&wmlspartner=wmtlabs&wl0=e&wl1=o&wl2=c&wl3=10364443495&wl4=kwd-1105707422888&wl12=21306294_0&wl14=quantum%20mechanics%20and%20hilbert%20space&veh=sem> Walmart </a>, apparently), which I read a few years ago. I won't look it up to see how many years ago because I don't want to get depressed.<br><br> So again, if you're looking for a memorable book on quantum mechanics, one that you'll grow into, pick up Anthony Sudbery's <I>Quantum Mechanics and the Particles of Nature</I>. Even if it did cost me two weeks wages when I was working at the drug store, I never regretted picking this gem up.PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-31229311355264928642017-07-25T20:29:00.001-07:002018-02-09T13:20:58.074-08:00Sleeping Beauties in Theoretical Physics: 26 Surprising Insights by Thanu Padmanahhan:<iframe style="width:120px;height:240px;" align = "right" marginwidth="0" marginheight="0" scrolling="no" frameborder="0" src="//ws-na.amazon-adsystem.com/widgets/q?ServiceVersion=20070822&OneJS=1&Operation=GetAdHtml&MarketPlace=US&source=ss&ref=as_ss_li_til&ad_type=product_link&tracking_id=physicsfm-20&marketplace=amazon®ion=US&placement=3319134426&asins=3319134426&linkId=01a3f0ad5ae35fb2ca0939c081d304f2&show_border=true&link_opens_in_new_window=true"></iframe>Thanu Padmanahhan's book, Sleeping Beauties in Theoretical Physics is a great find. It's reasonably accessible for a technical tome on theoretical physics, it has an interesting framework that makes the connections between chapters on very different subjects coherent, and it covers a number of interesting topics, including ones that I'd thought I'd have references to in other books but my knowledge of them must have come from papers. <br><br> The feature that Padmanabhan uses to categorize physics is similar to the one used by Griffiths in his Introduction to Electrodynamics: a cube has eight vertices, and each of these vertices is a type of physical theory. Each of the eight vertices has one of three Boolean values: gravitation, relativity, and quantum. If the effect is accounted for, the value is on, if not, it's off. The vertex where they are all off is Newtonian Mechanics (without gravity) and the far vertex is a Theory of Everything (or somesuch, he calls it something else). Turning gravity off is like setting the gravitational constant equal to zero, turning relativity off is like setting the speed of light to infinity, and turning quantum mechanics off is like setting Planck's constant equal to zero. <br><br> So, I could make a list of the different vertices:<br><br> <blockquote>(0,0,0) Newtonian Mechanics<br>(1,0,0) Newtonian Gravity<br>(0,1,0) Special Relativity<br>(0,0,1) Qunatum Mechanics<br>(1,1,0) General Relativity<br>(1,0,1) Gravitational Quantum Mechanics<br>(0,1,1) Quantum Field Theory</br>(1,1,1) Theory of Everything</blockquote><br><br> The most interesting statement in the introductory chapter is that GQM is a theoretically unpopular zone, and very poorly developed, despite being one step away from the TOE and possibly holding clues to it (or, I assume it would, even if it's boring to the high-powered mathematical physics wizards).<br><br> Sleeping Beauties touches on most of these topics (perhaps being short on the TOEs), showing up with some interesting takes on different phenomena, many of which I knew (rainbows and mirages, Thomas precession), many of which I didn't realize (the connection between Thomas precession and the Foucault pendulum), and many I had never touched on in my life (gravitational bending of the electric field). The twenty-six chapters have at least twenty-five topics and are each worthy of attention, especially those where he's making connections either between the vertices of his scheme or between subjects that seem disparate (but really aren't).<br><br> But, it's not for people who avoid mathematics.<br><br> The very first chapter of content, "The Emergence of Classical Physics," is an example of this. It tries to show how minimization principles in classical physics are explained by the limit of quantum mechanics. This uses Wigner functions to show that the action is the phase of the quantum mechanical wave function, and so classical particles follow trajectories that follow paths where the wave function's phases isn't cancelled out by neighboring paths (just like in Feynman's QED: The Strange Theory of Light and Matter). Obviously, if you're not up on the quantum mechanics or the calculus of variations, you might not see why this is so awesome. Speaking of QED, chapter 17, "If Quantum Mechanics is the Paraxial Optics, Then..." does something similar by applying the results of chapter 16's investigation of the transformation from wave optics to ray optics to discuss how quantum particles move in quantum field theory. Including why you must include trajectories for your particles that go backward in time. It's all the same process.<br><br> That is probably the most obvious recurring theme in the book: by understanding how a theory can be derived from a more fundamental theory, mysterious things like minimization principles can be made to make sense. That is, if you know how to turn off one of the switches, then you can better understand why things occur in the lower level theories -- and where those theories might lead you astray.<br><br> I therefore heartily recommend this book, and hope you both read and like it, but it does require an investment in mathematics to realize its physical returns.<br><br> ["I therefore heartily recommend..." Looks like I've been writing too many recommendation letters, again.]PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-24561266416319380412017-07-17T20:51:00.001-07:002017-09-06T11:22:19.334-07:00Screwing Up on Quantum ComputingWell, I screwed that up. <br /><br />In the next Physics Frontiers podcast, recorded about six months ago (approx. 1/27), Randy and I talked about photonics and quantum computing. The papers we read were very interesting and we had a good time talking about them, although we got a little bit confused (as my memory serves me, I believe that happens in the next episode as well). During the episode I went off on three digressions that I probably shouldn't have: science fiction, quantum computing, and economics and politics. I cut out all of the economics and politics bits (again). I left in the quantum computing, and that's what this is about.<br /><br />I first read a journal article and had discussions with reasonably technical people about quantum computing in the 90's, before 1998 and after 1995 based on the people I was talking to. The whole idea that someone could construct an algorithm for a computer of a type that didn't exist yet really intrigued me at that point, and since one of my majors was "theoretical mathematics" (I think that's what the track name for all that abstract algebra and number theory stuff was at that school), figuring things about like how to factor large numbers very quickly was interesting to me. The applications to cryptography, not so much. But, the state of the art at that time was a sheet of paper and a proof, so my marginal interest in the subject didn't really go anywhere.<br /><br />I've occasionally looked in on quantum computing from time to time since then. I've read a couple of technical books on the subject, for example, and I'll read articles about it when I actually have time to crack open one or two the Science and Nature magazines that clutter up my office. So, although I'm certainly not an expert (I'm not an expert about anything we talk about on Physics Frontiers), I certainly didn't think anything really astounding had happened. I was pretty sure a couple of people had put together a small number of qubits in one or the other of the ultracold settings.<br /><br />I had no idea that Google and IBM had them up and running.<br /><br />That's what my phone told me today, about lunchtime.<br /><br />I think that I had heard that <a href="http://www.quantumplayground.net/#/home">quantum computer simulators</a> existed, and so some of my comments were just thoughtless ("people who design algorithms for computers that don't exist and then mathematically prove they'll run correctly" or something like that), but the fact that <a href="https://www.research.ibm.com/ibm-q/">IBM has a 17 bit quantum processor</a> up and running and they're giving people beta access with an <a href="https://developer.ibm.com/code/2017/05/17/developers-guide-to-quantum-qiskit-sdk/">SDK for Python</a> makes some of my comments laughable. And of course, <a href="https://plus.google.com/+QuantumAILab">Google</a>'s up to the same thing.<br /><br />It's amazing how fast these things are developing.<br /><br />Oh well. The episode's already short, so I won't edit anything more out. You can just hear me babble from the past about things in the future.<br /><br />Now, how can I get into that IBM beta?PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-10353771569273938152017-06-30T21:12:00.001-07:002020-05-24T15:44:40.034-07:00List of Requirements for Gravitational TheoriesHere it is without fanfare. If you have any questions about any part of it, please comment in the comments:<br /><br /> <br />-------------------------------<br /><br />To be theoretically consistent and compatible with experiment, a theory of gravitation must: <br /><ol type="1"> <li>Predict correct cosmological dynamics </li> <ol type="a"><li> Big bang nucleosynthesis</li></ol> <li>Produce the correct evolution of cosmological perturbations</li> <ol type="a"><li>Cosmic microwave background</li> <li>Large scale structure</li></ol> <li>Have the correct weak-field limits</li> <ol type="a"><li>Reproduces Newtonian Mechanics</li> <li>Predicts post-Newtonian experiments in weak field</li> <li>Produces stable solutions</li> <ol type = i><li>Matter-side instabilities (Dolgov-Kawasaki)</li> <ol type="A"><li>Ground states should be highly symmetric</li></ol> <li>Gravity-side instabilities</li> <ol type="A"><li>Stable de Sitter solutions</li></ol> <li>Stability of the first loop in quantum gravity</li> <li>Stability in the face of inhomogeneous but isotropic perturbations</li> <li>Black hole nucleation</li> </ol> </ol> <li>Not contain any ghost fields </li> <li>Admit a well-posed Cauchy problem </li> <li>Reasonable theory of gravity waves <br /> </li></ol>PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-79731993259121962102016-10-31T20:21:00.000-07:002017-07-17T20:22:07.833-07:00Physics FrontiersRandy and I have started up a companion podcast, <a href = http://physicsfm-frontiers.blogspot.com/>Physics Frontiers</a>, with shorter discussions of topics in physics. <a href = http://physicsfm-frontiers.blogspot.com/>Check it out!</a> <iframe src='https://podomatic.com/embed/html5/episode/8242815?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe> Show notes at <a href = http://physicsfm-frontiers.blogspot.com/2016/10/g4v-gravitational-4-vector-formulation.html>the Physics Frontiers</a> website.PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-42920823846755921532015-08-04T16:40:00.000-07:002017-09-06T11:28:32.620-07:00Schrodinger's CatI've put together a video describing Schrodinger's cat and explaining why its important to have an interpretation of quantum mechanics. It doesn't give any answers, just explains why the question is so important. We overview some of the answers in the next podcast, which I will hopefully get up tomorrow (I'm putting in the breaks right now. I need to record the intro and upload it, so it's pretty likely).<br /><br />Plus, I drew the pictures.<br /><br /><iframe allowfullscreen="" frameborder="0" height="315" src="https://www.youtube.com/embed/VDJ1AsscO94" width="560"></iframe><br />PhysicsFMhttp://www.blogger.com/profile/13134018651176248475noreply@blogger.com0