tag:blogger.com,1999:blog-64723337249584678962019-01-20T03:23:58.056-08:00PhysicsFMJames Rantschlernoreply@blogger.comBlogger69125tag:blogger.com,1999:blog-6472333724958467896.post-63331954627238845602018-12-23T16:29:00.002-08:002018-12-23T16:29:35.252-08:00The Octonions<table style="width:100%"><tr><td align = left><a href = https://physicsfm-frontiers.blogspot.com/2018/12/negative-effective-mass.html><-- Previous (Negative Effective Mass)</a></td><td align = right> <text align = right>(Chameleon Field) Next --></text><br></td></tr></table><br><iframe src='https://podomatic.com/embed/html5/episode/8976221?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br>Recorded: 10/20/2018 Released: 12/23/2018 <br /><br><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Randy tells Jim about the octonions, a cousin to the complex numbers in eight dimensions that Cohl Furey has made some headlines with by categorizing elementary particles with them. By looking at, basically, stable sets in the octonions, she has found representations that act like the elementary particles, and found ways to characterize some of their parameters, e.g., the charge, with them.</span><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li> Furey, C., "<a href = https://journals.aps.org/prd/abstract/10.1103/PhysRevD.86.025024>Unified Theory of Ideals</a>" <I>Phys Rev D</I> <b>86</b>, 025024 (2012). [<a href =https://arxiv.org/abs/1002.1497>Free</a>] </li> <li> Furey, C, "<a href = https://www.sciencedirect.com/science/article/pii/S0370269318306452>Three Generations, Two Unbroken Gauge Symmetries, and One Eight-Dimensional Algebra</a>" <I>Phys Lett B</I> <b>785</b>, 84 (2018). [<a href = https://www.creol.ucf.edu/Research/Publications/7155.pdf>Free</a>] [<a href = https://media.nature.com/original/nature-assets/nphys/journal/v9/n12/extref/nphys2777-s1.pdf>Supplement</a>]</li> </ul><br>2. Related Papers: <br /><ul><li> Furey, C., "<a href = https://arxiv.org/abs/1611.09182>Standard Model Physics from an Algebra</a>" PhD. Thesis. <li> Baez, J., "<a href = http://www.ams.org/journals/bull/2002-39-02/S0273-0979-01-00934-X/home.html>The Octonions</a>." <I>Bull. Amer. Math. Soc.</I> <B>39</B> 145 (2002).</li><li> The <a href = https://www.quantamagazine.org/the-octonion-math-that-could-underpin-physics-20180720/>Quanta magazine</a> article that got Randy interested. </ul><br>3. Related Episodes of Physics Frontiers:<br><ul><li><a href = http://physicsfm-frontiers.blogspot.com/2018/09/the-string-theory-landscape.html>Physics Frontiers 35: The String Theory Landscape</a></li><li><a href = http://physicsfm-frontiers.blogspot.com/2018/05/the-consistent-histories-interpretation.html>Physics Frontiers 30: The Consistent Histories Interpretation of Quantum Mechanics</a></li></uL><br> <br><br>4. Books mentioned in this podcast:<br><ul><li>Crowe, Michael, <a href = https://amzn.to/2V6WQMP>A History of Vector Analysis</a>. A little bit dry, but a third of the book is about Hamilton and the quaternions.</li><li>Whitehead, A.N., <a href = https://amzn.to/2V5mdyi>Process and Reality</a>. If you think you're smart, try this.</li><li>Fano and Fano, <a href = https://amzn.to/2rQRR5d>Physics of Atoms and Molecules</a>. Lots of perturbations. That's what I remember.</li></ul><br> 5. John Baez' <a href = http://math.ucr.edu/home/baez/octonions/>webpage</a> for all things octonion.<Br><br>6. Cohl Furey's <a href - https://www.youtube.com/channel/UCvsmxUuD5ZdOGittaeosXMA>video series</a> on the octonions and the standard model.<br><br> 6. Please visit and comment on our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>, and if you can help us keep this going by contributing to our <a href = https://www.patreon.com/PhysicsFrontiers>Patreon</a>, we'd be grateful. <br><br><table style="width:100%"><tr><td align = left><a href = https://physicsfm-frontiers.blogspot.com/2018/12/negative-effective-mass.html><-- Previous (Negative Effective Mass)</a></td><td align = right> <text align = right>(Chameleon Field) Next --></text><br></td></tr></table><br>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-60807266295797176422018-10-16T12:46:00.000-07:002018-10-16T12:46:01.045-07:00The Metamaterial Stress Tensor<table style="width:100%"><tr><td align = left><a href = https://physicsfm-frontiers.blogspot.com/2018/09/the-string-theory-landscape.html><-- Previous (String Theory Landscape)</a></td><td align = right> <text align = right>(Einstein-Cartan Theory) Next --></text><br></td></tr></table><br><iframe src='https://podomatic.com/embed/html5/episode/8918483?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br>Recorded: 5/26/2018 Released: 10/14/2018 <br /><br><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Randy tells Jim about advances in the stress-momentum tensor of electrodynamics. This tensor can be integrated over the boundary of an object to describe the force on it from the magnetic field. It is closely related to the momentum carried in the electromagnetic field, and its proper formulation in materials has been the subject of debate for over a hundred years.</span><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li> Wang, S., J. Ng, C.T. Chan, "<a href = http://advances.sciencemag.org/content/2/3/e1501485.full>Electromagnetic Stress at the Boundary: Photon Pressure or Tension?</a>" <I>Science Advances</I> <b>2</b>, e1501485 (2016). [<a href = https://arxiv.org/abs/1510.06227>arXiv</a>]</li><li> Wang, N., S. Wang, J. Ng, "<a href = https://journals.aps.org/pra/abstract/10.1103/PhysRevA.97.033839>Electromagnetic Stress Tensor for Amorphous Metamaterial Medium</a>." <I>Phys Rev A</i> <b>97</b>, 033839 (2018). 1745-1749. [<a href = https://arxiv.org/abs/1801.00942>arXiv</a>]</li></ul><br> <br>2. Other papers mentioned:<br><br>I found these papers useful for this program:<br><ul><li>Brevik, I., "<a href = https://www.sciencedirect.com/science/article/abs/pii/0370157379900747>Expriments in Phenomenological Electrodynamics and the Electromagnetic Energy-Momentum Tensor</a>." <I>Phys Rep</I> <b>52</b> 133(1979). [<a href = http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.205.5763&rep=rep1&type=pdf>CiteSeerX</a>] </li><li>Barnett, S.M., and R. Loudon, "<a href =http://rsta.royalsocietypublishing.org/content/368/1914/927>The Enigma of Optical Momentum in a Medium</a>." <I>Phil Trans R Soc A</I> <b>368</b> 927(2010)</li></ul><br>3. Books mentioned in this podcast:<br><br><ul><li> J.D. Jackson's <a href = https://amzn.to/2pV02wA><I>Classical Electromagnetism</I></a>, discusses the Maxwell stress tensor twice: in a discussion about of conservation laws in macroscopic media (pp 239-40) and then in a discussion about forces in special relativity (pp 602-607). Page numbers from my copy of the 2nd edition.</li><li> Landau & Lifshitz' <a href = https://amzn.to/2pV02wA><I>Electrodynamics of Continuous Media</I></a> goes into more depth on how the stress tensor is derived. Beyond being one of my favorite books in grad school, the entire series is classic.</li><li> M. Schwartz' <a href = https://amzn.to/2pUZGpK><I>Principles of Electrodynamics</I></a> (available from Dover, probably because of Schwartz' Nobel Prize, not because its great exposition (which it has)) uses the electromagnetic stress tensor repeatedly in different contexts and problems that gives you a good idea of what it actually means.</li><li> U. Leonhardt and T. Philbin's <a href = https://amzn.to/2PGzOcc><I>Geometry and Light: The Science of Invisbility</I></a> is an excellent technical book of the use of the mathematics of general relativity in optics. This includes the optical analogue of black holes and the photonic Aharonov-Bohm effect. </li></ul>4. Related Shows:<br><br><ul><li></li></ul>5. Please visit and comment on our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>, and if you can help us keep this going by contributing to our <a href = https://www.patreon.com/PhysicsFrontiers>Patreon</a>, we'd be grateful. <br><br> <table style="width:100%"><tr><td align = left><a href = https://physicsfm-frontiers.blogspot.com/2018/09/the-string-theory-landscape.html><-- Previous (String Theory Landscape)</a></td><td align = right> <text align = right>(Einstein-Cartan Theory) Next --></text><br></td></tr></table><br>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-30367506412857370772018-09-22T19:09:00.002-07:002018-09-22T19:09:31.137-07:00The String Theory Landscape<table style="width:100%"><tr><td align = left><a href = http://physicsfm-frontiers.blogspot.com/2018/08/cpt-symmetry-and-gravitation.html><-- Previous (CPT Symmertry and Gravitation)</a></td><td align = right> <text align = right>(Metamaterial Stress Tensor) Next --></text><br></td></tr></table><br><iframe src='https://podomatic.com/embed/html5/episode/8899150?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br>Recorded: 5/12/2018 Released: 9/21/2018 <br /><br><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Jim and Randy explore the landscape of string theory, an idea put forward by Leonard Susskind about how to interpret the cornucopia of universes possible in string theory. </span><br /><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li> Susskind, L., "The Anthropic Landscape of String Theory" in Carr, Bernard (ed.), <a href = https://amzn.to/2xKbnD0><I>Universe or Multiverse?</I></a> (Cambridge, 2009), 247-266. [<a href = https://arxiv.org/abs/hep-th/0302219>arXiv</a>]</li><li> Susskind, L., "Supersymmetry Breaking in the Anthropic Landscape" in Shifman, Vainshtein, and Wheater (eds.) <I>From Fields to Strings: Circumnavigating Theoretical Physics</I> (World Scientific, 2005). 1745-1749. [<a href = https://arxiv.org/abs/hep-th/0405189>arXiv</a>]</li></ul>2. Books mentioned in this podcast:<br><br><ul><li> I reviewed <a href = http://physicsfm-master.blogspot.com/2018/04/cosmic-update-by-adams-buchert-and.html>Cosmic Update</a> some time ago.</li><li> I also reviewed the previous volume, <a href = http://physicsfm-master.blogspot.com/2017/10/extra-dimensions-in-space-and-time-by.html>Extra Dimensions in Space and Time,</a> which includes a nice explanation of Itzhak Bars' 2T theory.<li></ul>3. Previous shows mentioned in this podcast:.<br><br><ul><li> Physics Frontiers 18:<a href = http://physicsfm-frontiers.blogspot.com/2017/12/the-2t-physics-of-itzhak-bars.html>The 2T Physics of Itzhak Bars</a></li></uL><br><br>4. Related Shows:<br><br><ul><li> Physics Frontiers 23: <a href = http://physicsfm-frontiers.blogspot.com/2018/02/dark-energy.html>Dark Energy</a></li></ul>5. Please visit and comment on our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>, and if you can help us keep this going by contributing to our <a href = https://www.patreon.com/PhysicsFrontiers>Patreon</a>, we'd be grateful. <br><br> <table style="width:100%"><tr><td align = left><a href = http://physicsfm-frontiers.blogspot.com/2018/08/cpt-symmetry-and-gravitation.html><-- Previous (CPT Symmertry and Gravitation)</a></td><td align = right> <text align = right>(Metamaterial Stress Tensor) Next --></text><br></td></tr></table><br>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-12764610231763152962018-09-01T10:07:00.002-07:002018-09-22T19:09:51.392-07:00Quantum Sense and Nonsense by Jean Bricmont<a href="https://www.amazon.com/Quantum-Sense-Nonsense-Jean-Bricmont/dp/3319652702/ref=as_li_ss_il?s=books&ie=UTF8&qid=1535815705&sr=1-1&keywords=quantum+sense+and+nonsense&linkCode=li2&tag=physicsfm0a-20&linkId=e4a28d4f759191c26547a44edaf90ca5&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=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=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/2PWoHMX>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/2PWG4gv>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/2C9nO0V>Making Sense of Quantum Mechanics</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 and a science journalist a Motl 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), 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.James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-29908651541198204072018-08-10T15:16:00.002-07:002018-08-10T15:16:28.656-07:00CPT Symmetry and Gravitation<table style="width:100%"><tr><td align = left><a href = http://physicsfm-frontiers.blogspot.com/2018/07/retrocausality.html><-- Previous (Retrocausality)</a></td><td align = right> <text align = right>(The String Theory Landscape) Next --></text><br></td></tr></table><br><iframe src='https://podomatic.com/embed/html5/episode/8865067?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br>Recorded: 3/28/2018 Released: 8/10/2018 <br /><br><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Jim and Randy discuss what happens when CPT symmetry is applied to gravitation. CPT symmetry -- what happens to a theory when you reverse the sign of the charge, the handedness of a particle, and the direction of time evolution all at the same time -- is a basic tenet of the standard model. Massimo Villata has applied this symmetry to gravitation and has derived consequences for the way in which antimatter particles interact with gravity and various cosmological conclusions that follow from that. </span><br /><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li> Villata, M., "<a href = https://epljournal.edpsciences.org/articles/epl/abs/2011/08/epl13424/epl13424.html>CPT Symmetry and Antimatter Gravity in General Relativity</a>" EPL 94, 20001 (2011). [<a href = https://arxiv.org/abs/1103.4937>arXiv</a>]</li><li> Villata, M., "<a href = https://link.springer.com/article/10.1007%2Fs10509-012-0994-9>Dark Energy in the Local Void</a>" Astrophys Space Sci 339, 7 (2012). [<a href = https://arxiv.org/abs/1201.3810>arXiv</a>]</li></ul>2. I found these papers in the footnotes to Alberto Vecchiato's <a href = https://amzn.to/2vBOtxx>Variational Approach to Gravity Field Theories</a>.<br><br> 3. Please visit and comment on our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>, and if you can help us keep this going by contributing to our <a href = https://www.patreon.com/PhysicsFrontiers>Patreon</a>, we'd be grateful. <br><br> <table style="width:100%"><tr><td align = left><a href = http://physicsfm-frontiers.blogspot.com/2018/07/retrocausality.html><-- Previous (Retrocausality)</a></td><td align = right> <text align = right>(The String Theory Landscape) Next --></text><br></td></tr></table><br>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-68174224978393048382018-08-10T15:15:00.001-07:002018-08-10T15:15:42.166-07:00Retrocausality<table style="width:100%"><tr><td align = left><a href = http://physicsfm-frontiers.blogspot.com/2018/07/tunneling-time.html><-- Previous (Tunneling Time)</a></td><td align = right> <text align = right><a href = http://physicsfm-frontiers.blogspot.com/2018/08/cpt-symmetry-and-gravitation.html>(CPT Symmetry and Gravitation) Next --></a></text><br></td></tr></table><br><iframe src='https://podomatic.com/embed/html5/episode/8852279?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br>Recorded: 3/3/2018 Released: 7/25/2018 <br /><br><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Randy talks to Jim about retrocausality in quantum physics -- how does the future affect the past? In particular, they talk about the ideas of Huw Price and Ken Wharton on using temporal boundary conditions to constrain the wave function through its initial and final boundary conditions, effectively creating quantum harmonics in the time domain. They also discuss what this means in terms of the de Broglie-Bohm hypothesis, the multiple worlds interpretation, and Yakir Aharonov's interpretation in Quantum Paradoxes. </span><br /><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li> Wharton, K., "<a href = http://www.mdpi.com/2073-8994/2/1/272>Time Symmetric Boundary Conditions and Quantum Foundations</a>" Symmetry 2, 272 (2010). [<a href = https://arxiv.org/abs/1003.4273>arXiv</a>]</li><li> Price H, "<a href = https://www.sciencedirect.com/science/article/pii/S0370157314003159?via%3Dihub>Does Time-Symmetry Imply Retrocausality? How the Quantum World Says "Maybe"</a>" Studies in the History and Philosophy of Modern Physics B 43, 75 (2012). [<a href = https://arxiv.org/abs/1002.0906>arXiv</a>]</li><li> Evans, P., K. Wharton, and H. Price, "<a href = http://www.mdpi.com/2073-8994/2/1/272>New Slant on the EPR-Bell Experiment</a>" British Journal for the Philosophy of Science 64, 297 (2013). [<a href = https://arxiv.org/abs/1001.5057>arXiv</a>]</li><li> Leifer, M. and M. Pusey, "<a href = http://rspa.royalsocietypublishing.org/content/473/2202/20160607t>Is a time symmetric interpretation of quantum theory possible without retrocausality?</a>" Studies in the History and Philosophy of Modern Physics B 43, 297 (2012). [<a href = https://arxiv.org/abs/1607.07871v2>arXiv</a>]</li> </ul>2. Books discussed in the program:<br><ul><li> Aharonov, <a href = https://amzn.to/2uRbCeX>Quantum Paradox</a> [<a href = http://physicsfm-master.blogspot.com/2018/07/quantum-paradoxes-by-aharonov-and.html>PhysicsFMReview</a>]</li><li> Bohm, <a href = https://amzn.to/2mIaHsX>Quanatum Theory</a></li><li> Bell, <a href = https://amzn.to/2JWoBki>Speakable and Unspeakable in Qunatum Mechanics</a> [<a href = http://physicsfm-master.blogspot.com/2017/09/speakable-and-unspeakable-in-quantum.html>PhysicsFM Review</a>]</li><li> Goldstein, <a href = https://amzn.to/2LMbLqE>Classical Mechanics</a></li></uL> <br><br> 3. Huw Price also wrote a book about the philosophy of time called <a href https://amzn.to/2mTiyU>Time's Arrow and Archimedes' Point</a> that, according to the plane ticket I was using as a bookmark, I last read in 2003. <br><br>4. Please visit and comment on our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>, and if you can help us keep this going by contributing to our <a href = https://www.patreon.com/PhysicsFrontiers>Patreon</a>, we'd be grateful. <br><br> <table style="width:100%"><tr><td align = left><a href = http://physicsfm-frontiers.blogspot.com/2018/07/tunneling-time.html><-- Previous (Tunneling Time)</a></td><td align = right> <text align = right><a href = http://physicsfm-frontiers.blogspot.com/2018/08/cpt-symmetry-and-gravitation.html>(CPT Symmetry and Gravitation) Next --></a></text><br></td></tr></table><br>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-27491114097370305842018-08-02T19:54:00.000-07:002018-08-02T19:54:28.458-07:00Physics Frontiers: Most Popular EpisodesMost popular episodes, by downloads/month after 4 months. <br><br> 2017 The Physics of Time Travel<br>Vacuum Fluctuations and the Casimir Effect<br>f(R) theories of gravity<br><br> Physics Frontiers Index James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-64480260962021720502018-07-25T20:10:00.001-07:002018-07-25T20:10:38.498-07:00Quantum Paradoxes by Aharonov and RohrlichYou might think I like <a href =https://amzn.to/2LQkUOT>Quantum Paradoxes</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><a href="https://www.amazon.com/Quantum-Paradoxes-Theory-Perplexed/dp/3527403914/ref=as_li_ss_il?s=books&ie=UTF8&qid=1532574425&sr=1-1&keywords=quantum+paradoxes&linkCode=li2&tag=physicsfm0a-20&linkId=708b9aed290a955eca4681cff59fdb89&language=en_US" target="_blank"><img border="0" align = right src="//ws-na.amazon-adsystem.com/widgets/q?_encoding=UTF8&ASIN=3527403914&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=3527403914" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" />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. James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-15480748793153793672018-07-06T21:11:00.000-07:002018-07-06T21:11:07.488-07:00Tunneling Time<table style="width:100%"><tr><td align = left><a href = http://physicsfm-frontiers.blogspot.com/2018/06/the-parameterized-post-newtonian.html><-- Previous (Consistent Histories)</a></td><td align = right> <text align = right>(Retrocausality) Next --></text><br></td></tr></table><br><iframe src='https://podomatic.com/embed/html5/podcast/5495687?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br />Recorded: 11/25/2017 Released: 7/6/2018 <br /><br><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Jim and Randy discuss the tunneling time problem: just how long does quantum tunneling take? No definitive answer to this question exists, but people have been trying to answer it for at least eighty years -- with answers that span from instantaneous to subluminal. In this episode, we discuss several different ideas and how experiments at ETH-Zürich have helped clarify the issue. </span><br /><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li> Hauge, E.H., and J.A. Stovneng, "<a href = https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.61.917>Tunneling Times: A Critical Review</a>" Reviews of Modern Physics 61, 917 (1989). </li><li> Landsman, A.S., and U. Keller, "<a href = https://www.sciencedirect.com/science/article/pii/S0370157314003159?via%3Dihub>Attosecond Science and the Tunelling Time Problem</a>" Physics Reports 547, 1 (2015). [<a href = https://www.ethz.ch/content/dam/ethz/special-interest/phys/quantum-electronics/ultrafast-laser-physics-dam/publications_awards/publications/2015/383%20(PhysRep%20547,%201-24,%202015)%20as%20science%20and%20tunneling.pdf>ETH Zürich (free)</a>]</li> </ul>2. The <a href = http://www.ulp.ethz.ch/research/attoclock/tunneling-delay-time.html>group</a> responsible for the attoclock measurements at ETH-Zürich, including Landsman and Keller. <br><br>3. Please visit and comment on our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>, and if you can help us keep this going by contributing to our <a href = https://www.patreon.com/PhysicsFrontiers>Patreon</a>, we'd be grateful. <br><br> <table style="width:100%"><tr><td align = left><a href = http://physicsfm-frontiers.blogspot.com/2018/06/the-parameterized-post-newtonian.html><-- Previous (Post-Newtonian Gravity)</a></td><td align = right> <text align = right>(Retrocausality) Next --></text><br></td></tr></table><br>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-82565511149798594282018-06-15T19:37:00.003-07:002018-07-29T08:33:23.003-07:00Post-Newtonian Gravitation<table style="width:100%"><tr><td align = left><a href = http://physicsfm-frontiers.blogspot.com/2018/05/the-consistent-histories-interpretation.html><-- Previous (Consistent Histories)</a></td><td align = right> <text align = right>(Tunneling Time) Next --></text><br></td></tr></table><br><iframe src='https://podomatic.com/embed/html5/episode/8814306?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br />Recorded: 11/12/2017 Released: 6/8/2018 <br /><br><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Randy and Jim discuss the Parameterized Post-Newtonian Framework, a generalized way to compare metric theories of gravity to experiment in a standardized way. In this episode we discuss several theories of gravity and how they hold up under the light of experimental data. </span><br /><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br><center><text size = +1> A Guide to the Parameters</text> </center><br><br><ul><li>γ (gamma) - Coupling of matter to curvature, GR = 1 , Newton = 0</li><li>β (beta) - Linearity of superposition, GR = 1 - Superposition linear</li><li>ξ (xi) - Preferred location effects, GR = 0 - Spatially homogeneous</li><li>α<sub>1</sub> (alpha) - Preferred frame effects, GR = 0 - Lorentz invariant</li><li>α<sub>2</sub> (alpha) - Preferred frame effects, GR = 0 - Lorentz invariant</li><li>α<sub>3</sub> (alpha) - Preferred frame effects, GR = 0 - Lorentz invariant</li><li>ζ<sub>1</sub> (zeta) - Momentum changes, GR = 0 - Momentum conserved</li><li>ζ<sub>2</sub> (zeta) - Momentum changes, GR = 0 - Momentum conserved</li><li>ζ<sub>3</sub> (zeta) - Momentum changes, GR = 0 - Momentum conserved</li><li>ζ<sub>4</sub> (zeta) - Momentum changes, GR = 0 - Momentum conserved</li></ul><br /><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The paper we read for this program (only sections 3 and 4): <br /><ul><li> Griffiths, R., "<a href = https://link.springer.com/article/10.12942/lrr-2014-4>The Confrontation between General Relativity and Experiment</a>" Living Rev. Relativ. 17:4 (2014). [<a href = https://arxiv.org/abs/1403.7377>arXiv</a>]</li> </ul>2. My review of <a href = http://physicsfm-master.blogspot.com/2017/09/theory-and-experiment-in-gravitational.html>Will's book</a>. This paper serves as something of an update of it. A <a href = https://amzn.to/2uZMH9c>true update</a> is scheduled to come in December 2018. <br><br>3. Related Episodes of Physics Frontiers:<br><ul><li>Physics Frontiers 33: The Positive Energy Theorem</li><li><a href = http://physicsfm-frontiers.blogspot.com/2018/05/gravitational-alternatives-to-dark.html> Physics Frontiers 29: Gravitational Alternatives to Dark Energy</a></li><li><a href =http://physicsfm-frontiers.blogspot.com/2018/04/the-gravitational-equivalence-principles.html>Physics Frontiers 27: Gravitational Equivalence Principles</a></li><li><a href = http://physicsfm-frontiers.blogspot.com/2018/02/dark-energy.html>Physics Frontiers 23: Dark Energy</a></li><li><a href = http://physicsfm-frontiers.blogspot.com/2017/06/requirements-for-gravitational-theories.html>Physics Frontiers 10: Requirements for Gravitational Theories</a></li><li><a href = http://physicsfm-frontiers.blogspot.com/2017/06/fr-theories-of-gravity.html>Physics Frontiers 9: f(R) Theories of Gravity</a></li></uL><br>4. If you have any information about good packages for numerical relativity for Randy, please leave them in the comments.<br><br>5. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. <br><br> <table style="width:100%"><tr><td align = left><a href = http://physicsfm-frontiers.blogspot.com/2018/05/the-consistent-histories-interpretation.html><-- Previous (Consistent Histories)</a></td><td align = right> <text align = right>(Tunneling Time) Next --></text><br></td></tr></table><br>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-2279299967224228602018-05-24T08:27:00.000-07:002018-05-24T08:27:01.269-07:00The Consistent Histories Interpretation of Quantum Mechanics<iframe src='https://podomatic.com/embed/html5/episode/8800143?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br />Recorded: 10/29/2017 Released: 5/24/2018 <br /><br><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Jim and Randy investigate the Consistent Histories interpretation of quantum mechanics. This highly logical interpretation was conceived of by Robert Griffiths and is based on bundling possible histories for a particle together and only using those histories that are consistent with the measurements we perform to winnow out the possible states of the particle. Although Griffiths calls this "Copenhagen done right," the interpretation is based on the idea the quantum particles have definite values for observables in the intervening space. </span><br /><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li> Griffiths, R., "<a href = https://aapt.scitation.org/doi/10.1119/1.3606371>EPR, Bell, and Quantum Locality.</a>" Am J Phys 79, 954 (2011). [<a href = https://arxiv.org/abs/1007.4281>arXiv</a>]</li><li> Griffiths, R. "<a href = https://www.sciencedirect.com/science/article/pii/S1355219815000489> Consistent Quantum Measurements.</a>" Stud Hist Philos Sci B 52, 188 (2015). [<a href = tps://arxiv.org/abs/1501.04813>arXiv</a>]</li></ul><br>2. Griffith's book <a href = https://amzn.to/2GKMzxs>Consistent Quantum Theory</a>, which we mention in the podcast because he continually refers to it in the podcast. <br><br> 3. <A href = http://physicsfm-master.blogspot.com/2017/09/speakable-and-unspeakable-in-quantum.html>My review</a> of <a href = https://amzn.to/2ILFcYq><i>Speakable and Unspeakable in Quantum Mechanics</I></a> by John Bell, which includes the paper in which he formulates Bell's Theorem -- the testable version of the EPR Paradox, which is based on the first tractable formulation of the paradox by <a href = https://amzn.to/2J4T4QJ>David Bohm</a>. I also recently reviewed a book on <a href = http://physicsfm-master.blogspot.com/2018/05/the-wave-function-essays-on-metaphysics.html>wave function realism</a>, which seems to be a response to a response to Bell. <br><br>4. I haven't quite got the <a href = https://www.patreon.com/PhysicsFrontiers>Patreon</a> I promised Randy in this episode up and running, but it is at least limping.<br><br>5. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. <br><br>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-65522901107015082452018-05-22T20:26:00.001-07:002018-07-28T19:44:05.286-07:00The Wave Function: Essays on the Metaphysics of Quantum Mechanics<br /><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";"><a href = https://amzn.to/2mN85tQ>The Wave Function: Essays on the Metaphysics of Quantum Mechanics</a>, Ney and Albert, Eds.</span></div><a href="https://www.amazon.com/Wave-Function-Metaphysics-Quantum-Mechanics/dp/019979054X/ref=as_li_ss_il?_encoding=UTF8&me=&qid=1532832143&linkCode=li2&tag=physicsfm0a-20&linkId=dc191843584a8d5bf78e40a0415df43a&language=en_US" target="_blank"><img border="0" align = right src="//ws-na.amazon-adsystem.com/widgets/q?_encoding=UTF8&ASIN=019979054X&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=019979054X" width="1" height="1" border="0" alt="" style="border:none !important; margin:0px !important;" /><br /><div style="margin: 0px 0px 10.66px;"><span style="font-family: "calibri";">This 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>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-4789497554642368052018-05-15T19:53:00.002-07:002018-05-15T19:59:12.007-07:00Gravitational Alternatives to Dark Energy<iframe src='https://podomatic.com/embed/html5/episode/8792891?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br />Recorded: 10/15/2017 Released: 5/15/2018 <br /><br><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Jim and Randy discuss the ways in which different modified gravities mimic the observed dark energy in the universe, contra a cosmological constant hypothesis. They talk about various forms of modified gravity theories and the particles associated with their "fifth fields." </span><br /><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li> Carroll, S., Vikram, D., Trodden, M., and Turner, M., "<a href = https://journals.aps.org/prd/abstract/10.1103/PhysRevD.70.043528>Is Cosmic Speed-Up Due to New Gravitational Physics.</a>" Phys Rev D 70, 043528(R) (2005). [<a href = https://arxiv.org/abs/astro-ph/0306438>arXiv</a>]</li><li> Joyce, A., Lombriser, L., and Schmidt, F. "<a href =https://www.annualreviews.org/doi/10.1146/annurev-nucl-102115-044553> Dark Energy Versus Modified Gravity.</a>" Annu. Rev. Nuc. Part. Sci. 66, 95 (2016). [<a href = https://arxiv.org/abs/1601.06133>arXiv</a></li></ul><br>2. My review of <a href = http://physicsfm-master.blogspot.com/2017/09/theory-and-experiment-in-gravitational.html>Will's book</a>, which I talk about a little too much in this podcast. <br><br>3. Related Episodes of Physics Frontiers:<br><ul><li>Physics Frontiers 33: The Positive Energy Theorem</li><li>Physics Frontiers 31: The Parameterized Post-Newtonian Formalism</li><li><a href =http://physicsfm-frontiers.blogspot.com/2018/04/the-gravitational-equivalence-principles.html>Physics Frontiers 27: Gravitational Equivalence Principles</a></li><li><a href = http://physicsfm-frontiers.blogspot.com/2018/02/dark-energy.html>Physics Frontiers 23: Dark Energy</a></li><li><a href = http://physicsfm-frontiers.blogspot.com/2017/06/requirements-for-gravitational-theories.html>Physics Frontiers 10: Requirements for Gravitational Theories</a></li><li><a href = http://physicsfm-frontiers.blogspot.com/2017/06/fr-theories-of-gravity.html>Physics Frontiers 9: f(R) Theories of Gravity</a></li><li><a href = http://physicsfm-frontiers.blogspot.com/2017/06/fr-theories-of-gravity.html>Physics Frontiers 1: G4V: The Gravitational 4-Vector Formulation of Gravity</a></li></ul><br>4. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. <br><br>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-44375070841452766892018-04-25T19:47:00.001-07:002018-04-25T19:47:40.867-07:00The Quantum Vacuum and the Casimir Effect<iframe src='https://podomatic.com/embed/html5/episode/8773811?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br />Recorded: 9/16/2017 Released: 4/24/2018 <br /><br><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Jim and Randy review two very convincing papers that make the claim that the Casimir effect is due to materials fluctuations and not the zero point energy </span><br /><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li> Jaffe, R.L. "<a href = https://journals.aps.org/prd/abstract/10.1103/PhysRevD.72.021301>The Casimir Effect and the Quantum Vacuum.</a>" Phys Rev D 72, 021301(R) (2005). [<a href = https://arxiv.org/abs/hep-th/0503158>arXiv</a>]</li><li> Nikolic, N., "<a href = https://www.sciencedirect.com/science/article/pii/S0003491617301410> Is Zero-point Energy Physical? A Toy Model for Casimir-like Effect.</a>" Ann Phys 383, 181 (2017). [<a href = https://arxiv.org/abs/1702.03291>arXiv</a></li></ul><br>2. We discuss an earlier episode on<a href = http://physicsfm-frontiers.blogspot.com/2017/05/vacuum-fluctuations-and-casimir-effect.html> the Casimir Effect and van der Waals forces</a> repeatedly in this episode.<br><br>3. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. <br><br>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@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>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@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.James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-79664925070204354332018-04-14T18:59:00.001-07:002018-04-14T18:59:03.015-07:00The Gravitational Equivalence Principles<iframe src='https://podomatic.com/embed/html5/episode/8764498?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br />Recorded: 6/17/2017 Released: 3/25/2017 <br /><br><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Jim talks to Randy about the different ways in which the equivalence principle of general relativity can be formulated. More than just the equivalence of accelerations, the different possible meanings of the equivalence principle mean different things about how gravity works. From weak to strong, from Einstein's equivalence principle to Schiff's conjecture, the implications of these theories are explored. </span><br /><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li>Sotiriou, T., Faraoni, V., and Liberati, S, "<a href = https://www.worldscientific.com/doi/abs/10.1142/S0218271808012097>Theory of Gravitation Theories: A No Progress Report.</a>"Intl J Mod Phys D 17, 399 (2008). [<a href = https://arxiv.org/abs/0707.2748>arXiv</a>]</li><li>Di Casola, E. and Liberati, S, "<a href = https://aapt.scitation.org/doi/10.1119/1.4895342>Nonequivalence of Equivalence Principles.</a>" Am J Phys 83, 39 (2015). [<a href = https://arxiv.org/abs/1310.7426>arXiv</a></li></ul><br><br />2. My review of <a href = http://physicsfm-master.blogspot.com/2017/09/theory-and-experiment-in-gravitational.html>Will's book</a>, which I talk about a little too much in this podcast. <br><br>3. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-45586397208799736332018-03-25T16:59:00.002-07:002018-03-25T19:42:02.127-07:00Antimatter Production at a Potential Boundary<iframe src='https://podomatic.com/embed/html5/podcast/5495687?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br />Recorded: 6/17/2017 Released: 3/25/2017 <br /><br><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Randy discusses a proposal for the production of antimatter without using supercolliders with Jim. This proposal would have used Klein's paradox for the production of electron-positron pairs at a very sharp, steep potential boundary produced through the Casimir effect. </span><br /><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The paper we read for this program: <br /><ul><li>Lapointe, M., "<a href = https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20010091016.pdf>Antimatter Production at a Potential Boundary.</a>" NASA/CR 2001-211116 (2001).</li></ul><br><br />2. The <a href = http://www.niac.usra.edu/>NASA Institute for Advanced Concepts</a> no longer exists (apparently it closed down in 2007), but there is now a <a href = https://www.nasa.gov/directorates/spacetech/niac/index.html>NASA Innovative Advanced Concepts</a>, a program with the same acronym that seems to have a similar purpose (if not, tell me the salient difference in the comments). <br><br>3. Our listenership has increased markedly since we recorded this episode last June. We had 1,057 downloads in the first fifteen days of June 2017, and in the first two weeks of March we had 3,117. In both cases there were no podcasts published during the time interval (in the current case because this is my heavy semester at work and it eats into my free time). <br><br>4. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-67413490980404286802018-03-16T20:31:00.000-07:002018-07-28T19:54:57.795-07:00The 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>James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-19952088659849300782018-02-23T20:42:00.002-08:002018-02-23T20:42:13.615-08:00The Island of Stability<iframe src='https://podomatic.com/embed/html5/episode/8716081?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br /><br /><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Randy tells Jim about the Island of Stability. This is a theoretically predicted region (or two, in one calculation) where the isotopes of atoms with heavy nuclei are stable. Jim and Randy talk about the islands, how they are attempting to get there, and some of the calculations people use to predict the stability of elements. Along the way, they mispronounce a lot of words. </span><br /><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li>Karpov, A.V.,Zagrebaev, V.I., Martinez Palenzuela, Y., Felipe Ruiz, L., and Greiner, W., "<a href = http://www.worldscientific.com/doi/abs/10.1142/S0218301312500139?journalCode=ijmpe>Decay Properties and Stability of Heaviest Elements.</a>" International Journal of Modern Physics E 21, 1250013 (2012).</li><li>Oganessian, Y.T., "Synthesis of a New Element with Atomic Number Z = 117." Physical Review Letters 104, 142502 (2010).</li><li>Zagrebaev, V., Karpov, A., and Geiner, W., "<a href = http://iopscience.iop.org/article/10.1088/1742-6596/420/1/012001/meta>Future of Superheavy Element Research: Which Nuclei Could Be Synthesized within the Next Few Years?</a>" Journal of Physics Conference Series 420 012001 (2013) [<a href = https://arxiv.org/abs/1207.5700>arXiv</a>]</ul>2. The book I talked about on fluids that goes into the fluid model of the nucleus is <a href = http://amzn.to/2HGeOyO>Introduction to the Physics of Fluids and Solids</a> by James S. Trefil, which is apparently no longer in print (I have a Dover edition, I love Dover). My favorite Modern Physics text is <a href = http://amzn.to/2FtJR07>Rohlf</a>, mostly because of its focus on scattering, but I taught from <a hreef = http://amzn.to/2GEDFSi>Serway</a>, which is more standard. <br /><br><br />3. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-8171002016513654272018-02-08T19:40:00.001-08:002018-02-08T19:40:25.622-08:00Dark Energy<iframe src='https://podomatic.com/embed/html5/episode/8701690?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br /><br /><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Randy helps Jim get a handle on dark energy. Why do we need it? Why do we want to believe in it now, but didn't earlier? How many different things could it be? What does it have to do with you? How close are we to knowing anything about it? </span><br /><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li>Carroll, S., "Dark Energy and the Preposterous Universe." [<a href="https://arxiv.org/abs/astro-ph/0107571">arXiv</a>]</li><li>Turner, M., "Dark Energy and the New Cosmology." [<a href="https://arxiv.org/abs/astro-ph/0108103">arXiv</a>]</li><li>Zwicky, F., "On the Masses of Nebulae and Clusters of Nebulae." <i>Astrophys. J.</i> <b>86</b>, 217 (1937) [<a href="https://ned.ipac.caltech.edu/level5/Sept01/Zwicky/Zwicky_contents.html">web</a>]</li><li>Holsclaw, T., Alam, U., Sanso, B, Lee, H., Heitmann, K., Habib, S. and Higdon, D., "New Constraints on the Time-Variation of the Dark Energy Equation of State from Current Supernova Data." [<a href="https://www.soe.ucsc.edu/sites/default/files/technical-reports/UCSC-SOE-10-01.pdf">web</a>]</li></ul>2.I'll review Oyvind Gron's book, <I>Lecture Notes on the General Theory of Relativity</I> soon. I've been meaning to for a couple of months now.<br /><br>3. Previous Episodes Referenced:<br /><ul><li><a href = http://frontiers.physicsfm.com/7>Virtual Gravitational Dipoles</a></li><li><a href = http://frontiers.physicsfm.com/9>f(R) Theories of Gravity</a></li><li><a href = http://frontiers.physicsfm.com/10>Requirements for Alternative Theories of Gravity</a></li></ul>4.If you or Dragan Hejdukovic wants to supply us with the background energy that would be predicted from virtual gravitational dipoles, please leave us a nice comment with smilies.<br /><br />5. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-14594681149011500092018-01-23T11:52:00.001-08:002018-01-24T10:31:47.714-08:00Weyl and Quasiparticles<iframe allowfullscreen="" frameborder="0" height="208" marginheight="0" marginwidth="0" scrolling="no" src="https://podomatic.com/embed/html5/episode/8683635?autoplay=false" width="504"></iframe><br /><br /><span style="background-color: white; color: #525252; display: inline; float: none; font-family: "helvetica neue" , "helveticaneue" , "helvetica" , "arial" , sans-serif; font-size: small; font-style: normal; font-weight: 400; letter-spacing: normal; text-align: left; text-indent: 0px; text-transform: none; white-space: pre-line; word-spacing: 0px;">Jim and Randy discuss quasiparticles recently found in condensed matter systems that mirror particles theorized nearly a hundred years ago, but never found in the vacuum. Weyl particles are massless fermions, and once it was hoped that neutrinos would turn out to be this kind of particle, and Majorana fermions have real-valued wave functions and therefore many strange and possibly useful properties. </span><br /><b></b><i></i><u></u><sub></sub><sup></sup><strike></strike><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li>Pal, P.B., "Dirac, Majorana, and Weyl Fermions." Am. J. Phys. 79, 485 (2011).</li><li>Mourik, Zuo, Frolov, Plissard, Bakkers, and Kouwenhoven, "Signatures of Majorana Fermions in Hybrid Superconductor-Semiconductor Nanowire Devices." Science 336, 1003 (2012). [arXiv]</li><li>Nadj-Perge, Drozdov, Li, Chen, Jeon, Seo, MacDonald, Bernevig, and Yazsdani, "Observation of Majorana Fermions in Ferromagnetic Atomic Chains of a Superconductor." Science 346, 602 (2014) [arXiv] </li><li>Xu, et al., "Discovery of a Weyl Fermion State with Fermi Arcs in Niobium Arsenide." Nat. Phys. 11, 748 (2015) [arXiv]</li><li>Zhang, et al, Signatures of the Adler-Bell-Jackiw Chiral Anomaly in a Weyl Fermion Semimetal." Nat. Comm. 10735 (2016) [arXiv]</li></ul>2. Popular papers we may have read:<br /><ul><li>Wilczek, F., "Why are there Analogies between Condensed Matter and Particle Theory?" Physics Today, January 1998, 11.</li><li>Wilczek, F., "Majorana Returns." Nature Physics 5, 614 (2009)</li><li>Balents, Leon, "Weyl Electrons Kiss." Physics 4, 36 (2011).</li><li>"After a Weyl" Nat. Phys. 11, 697 (2015)</li><li>Bernevig, B.A., "Weyl Electrons Kiss." Nat. Phys. 11, 699 (2015)</li></ul>3. Original Papers:<br /><ul><li>Weyl, H., "Gravitation and the Electron." ..., 323 (1929).</li><li>Majorana, "A Symmetric Theory of Electrons and Positrons." Il Nuovo Cimento, 14, 171 (1937).</li></ul>4. I was wrong. "Weyl" rhymes with "pile," not with "pail."<br /><br />5. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. James Rantschlerhttps://plus.google.com/104496580781469381673noreply@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.James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-79468487966933723692018-01-10T19:45:00.000-08:002018-01-10T19:45:02.587-08:00The Origin of Inertia<iframe src='https://podomatic.com/embed/html5/episode/8673771?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe><br /><br />Randy tells Jim about a scheme that uses Mach's Principle - the idea that there is a preferred background frame with respect to the fixed stars - to explain the origin of inertia. Why exactly does an object in motion stay in motion? <br /><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li><a href = https://physics.fullerton.edu/~jimw/general/inertia/index.htm> The Origin of Inertia </a>, James Woodward (blog post, 1998)</li><li><a href = http://adsabs.harvard.edu/full/1953MNRAS.113...34S>On the Origin of Inertia</a>, Sciama, D. W., Monthly Notices of the Royal Astronomical Society 113, 34 (1953)</li><li><a href = https://www.hindawi.com/journals/amp/2013/801574/>Study on Inertia as a Gravity Induced Property of Mass, in an Infinite Hubble Expanding Universe</a>,Jeroen van Engelshoven, Advances in Mathematical Physics 2013, 801574 (2013)</li><li><a href = http://frankwilczek.com/Wilczek_Easy_Pieces/342_Origin_of_Mass.pdf>On the Origin of Mass</a>, Wilczek, F.</li></ul><br>2. In addition, Randy sent me a lot of blog and other forum posts for background:<br><ul><li> https://www.physicsforums.com/threads/the-origin-of-inertia.440707/</li><li> <A href = https://www.physicsforums.com/threads/origin-of-inertia.657760/>https://www.physicsforums.com/threads/origin-of-inertia.657760/</a></li><li> <a href = http://stardrive.org/stardrive/index.php/all-blog-articles/4846-sciamas-1952-paper-on-the-qorigin-of-inertiaq>http://stardrive.org/stardrive/index.php/all-blog-articles/4846-sciamas-1952-paper-on-the-qorigin-of-inertiaq</a></li><li> <a href = http://stardrive.org/stardrive/index.php/all-blog-articles/12297-james-f-woodward-s-book-making-starships-and-stargates-march-10-2014> http://stardrive.org/stardrive/index.php/all-blog-articles/12297-james-f-woodward-s-book-making-starships-and-stargates-march-10-2014</a></li><li> <a href = https://quantumj13.imascientist.org.uk/2013/06/19/is-higgs-field-an-answer-to-the-property-of-inertia-and-whats-the-role-of-higgs-boson-in-it/>https://quantumj13.imascientist.org.uk/2013/06/19/is-higgs-field-an-answer-to-the-property-of-inertia-and-whats-the-role-of-higgs-boson-in-it/</a></li></ul><br /><br />3. Our discussion on <a href = http://physicsfm-frontiers.blogspot.com/2016/12/gravitoelectromagnetism.html>Gravitoelectromagnetism</a>..<br><br>4. Our discussion of Aharonov and Rohrlich's <a href = https://paradoxes-physicsfm.blogspot.com/>Quantum Paradoxes</a>, nine of the ten recorded episodes. I don't think we get into the retrocausal part of it.<br><br>5. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0tag:blogger.com,1999:blog-6472333724958467896.post-80109199432278414602017-12-21T20:02:00.002-08:002017-12-21T20:03:16.330-08:00Time Crystals<iframe src='https://podomatic.com/embed/html5/episode/8657663?autoplay=false' height='208' width='504'frameborder='0' marginheight='0' marginwidth='0' scrolling='no' allowfullscreen></iframe> <br /><br />Jim talks to Randy about structures that are periodic in time like crystals are periodic in space. This idea came from Frank Wilczek in 2012, and was realized just recently, providing an extraordinary turn-around time from theory to observation. <br /><br />-------------------------------------------<br /><br />Notes:<br /><br />1. The papers we read for this program: <br /><ul><li><a href="https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.109.16040l">Quantum Time Crystals</a>, Wilczek,, F. <I> Physical Review Letters</I> <b>109</b>, 160401 (2012) [<a href="https://arxiv.org/abs/1202.2539">arXiv</a>] </li><li><a href = https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.118.030401>Discrete Time Crystals: Rigidity, Criticality, and Realizations</a>,Yao, Potter, Potirniche, and Vishwanath. <I> Physical Review Letters</I><b>119</b> 030401 (2017) [<a href="https://arxiv.org/abs/1608.02589">arXiv</a>]</li><li><a href="https://www.nature.com/articles/nature21413">Observation of Discrete Time Crystal</a>, Zhang, Hess, Kyprianidis, Becker, Lee, Smith, Pagano, Potirniche, Potter, Vishwanath, Yao, and Monroe. <I>Nature</I> <B>543</B> 217 (2017) [<a href="https://arxiv.org/abs/1609.08684">arXiv</a>] </li><li><a href="https://www.nature.com/articles/nature21426">Observation of discrete time-crystalline order in a disordered dipolar many-body system</a>, Zhang, Hess, Kyprianidis, Becker, Lee, Smith, Pagano, Potirniche, Potter, Vishwanath, Yao, and Monroe. <I>Nature</I> <B>543</B> 221 (2017) [<a href="https://arxiv.org/abs/1610.08057">arXiv</a>] </li></ul><br />2. Our <a href="https://www.reddit.com/r/physicsFM/">subreddit</a>. James Rantschlerhttps://plus.google.com/104496580781469381673noreply@blogger.com0