Friday, February 23, 2018

The Island of Stability



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.

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Notes:

1. The papers we read for this program:
2. The book I talked about on fluids that goes into the fluid model of the nucleus is Introduction to the Physics of Fluids and Solids 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 Rohlf, mostly because of its focus on scattering, but I taught from Serway, which is more standard.


3. Our subreddit.

Thursday, February 8, 2018

Dark Energy



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?

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Notes:

1. The papers we read for this program:
  • Carroll, S., "Dark Energy and the Preposterous Universe." [arXiv]
  • Turner, M., "Dark Energy and the New Cosmology." [arXiv]
  • Zwicky, F., "On the Masses of Nebulae and Clusters of Nebulae." Astrophys. J.  86, 217 (1937) [web]
  • 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." [web]
2.I'll review Oyvind Gron's book, Lecture Notes on the General Theory of Relativity soon. I've been meaning to for a couple of months now.

3. Previous Episodes Referenced:
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.

5. Our subreddit.

Tuesday, January 23, 2018

Weyl and Quasiparticles



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.

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Notes:

1. The papers we read for this program:
  • Pal, P.B., "Dirac, Majorana, and Weyl Fermions." Am. J. Phys. 79, 485 (2011).
  • Mourik, Zuo, Frolov, Plissard, Bakkers, and Kouwenhoven, "Signatures of Majorana Fermions in Hybrid Superconductor-Semiconductor Nanowire Devices."  Science 336, 1003 (2012). [arXiv]
  • 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]
  • Xu, et al., "Discovery of a Weyl Fermion State with Fermi Arcs in Niobium Arsenide." Nat. Phys.  11, 748 (2015) [arXiv]
  • Zhang, et al, Signatures of the Adler-Bell-Jackiw Chiral Anomaly in a Weyl Fermion Semimetal." Nat. Comm. 10735 (2016) [arXiv]
2.  Popular papers we may have read:
  • Wilczek, F., "Why are there Analogies between Condensed Matter and Particle Theory?" Physics Today, January 1998, 11.
  • Wilczek, F., "Majorana Returns." Nature Physics 5, 614 (2009)
  • Balents, Leon, "Weyl Electrons Kiss." Physics 4, 36 (2011).
  • "After a Weyl" Nat. Phys.  11, 697 (2015)
  • Bernevig, B.A., "Weyl Electrons Kiss." Nat. Phys. 11, 699 (2015)
3. Original Papers:
  • Weyl, H., "Gravitation and the Electron." ..., 323 (1929).
  • Majorana, "A Symmetric Theory of Electrons and Positrons." Il Nuovo Cimento, 14, 171 (1937).
4. I was wrong.  "Weyl" rhymes with "pile," not with "pail."

5. Our subreddit.

Monday, January 22, 2018

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Wednesday, January 10, 2018

The Origin of Inertia



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?

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Notes:

1. The papers we read for this program:

2. In addition, Randy sent me a lot of blog and other forum posts for background:


3. Our discussion on Gravitoelectromagnetism..

4. Our discussion of Aharonov and Rohrlich's Quantum Paradoxes, nine of the ten recorded episodes. I don't think we get into the retrocausal part of it.

5. Our subreddit.

Thursday, December 21, 2017

Time Crystals



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.

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Notes:

1. The papers we read for this program:

2. Our subreddit.

Wednesday, December 6, 2017

The 2T Physics of Itzhak Bars



Randy tells Jim about a theory that complements other theories of fundamental physics based upon a phase space symmetry between the 4-position and the 4-momentum of a particle. The upshot of the theory is that there should be a second time dimension and a fourth space dimension, both macroscopic in extent, and the physics we see are 4D projections from the larger 6D space-time.

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Notes:

1. The papers we read for this program:
  • A two Time Universe?, by Tom Siegfried on phys.org. This is a popular article on the theory.
  • The Standard Model as a 2T Physics Theory, Itzhak Bars. AIP Conference Proceedings 903, 550 (2006) [arXiv]
  • Gravity in 2T Physics, Itzhak Bars, Physical Review D77, 125027 (2008) [arXiv]

2. Itzhak Bars lecture on 2T Physics.

3. Extra Dimensions in Space and Time, a book containing a longer, less technical (almost popular) description of 2T physics by Itzhak Bars. That takes up about half the book, the other half is John Terning discussing more traditional extra dimensions in string theory. My review on PhysicsFM is here.

4. Our subreddit.