Sunday, December 9, 2018

Negative Effective Mass

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Recorded: 9/29/2018 Released: 12/9/2018

Randy introduces Jim to gravitational effects on quasiparticles in materials. The inertial quality of the mass of a quasiparticle gets modified by the lattice, giving rise to an effective mass in the material. But how does the effective mass behave when confronted with a gravitational field?
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Notes:

1. The papers we read for this program:

2. Related Papers:

2. Related Episodes of Physics Frontiers:

We referenced a lot of old episodes in this one:

Don't bother looking for our discussion of Manu Paranjape's essays on the "possibility of generating an negative effective mass in space-time" in the episode entitled "The Positive Energy Theorem." We're working on getting those up, but there's a content issue that we may not be able to resolve.

3. Books mentioned in this podcast:
  • I mentioned that some of this is textbook stuff, when Jim Napolitano finished J.J. Sakurai's Modern Quantum Mechanics, he included he discusses Colletta, Overhauser and Werner's gravity induced phase changes that can be measured through interferometry. Somewhere Napolitano writes that he includes these interesting tidbits because he is an experimentalist and thinks it's helpful for understanding. I just know they're fun. Be advised that, although it's not as heavy going as Cohen-Tannoudji (which, thanks only to the trauma induced by graduate school, I somehow spelled right), is a graduate level quantum mechanics textbook. Just a very well written one.

4. You can watch Martin Tejmar's talk at the 2016 breakthrough propulsion workshop put on by the Space Studies Institute

5. Martin Tejmar's group at TU-Dresden, and his publications page.

6. Please visit and comment on our subreddit, and if you can help us keep this going by contributing to our Patreon, we'd be grateful.

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Sunday, November 25, 2018

The Dimensionality of Space Time

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Recorded: 9/8/2018 Released: 11/25/2018

Jim and Randy discuss why space-time is four dimensional. Much of what they discuss is anthropic in nature: what sort of universe can we exist in? But they also discuss the stability of orbits, the predictability of nature, and so on, all of which constrain the universe to have three (3) macroscopic dimensions of space and one of time (or one of space and three of time, but that's not us).
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Notes:

1. The papers we read for this program:

2. Other papers mentioned in this program:

3. Related Episodes of Physics Frontiers:

4. Books mentioned in the podcast:
  • Tegmark talked about results discussed in Gravitation by Misner, Thorne and Wheeler. This is a standard text in the field, which I'm sad to say I never picked up. Although I did order a copy last week, and its on its way to my office right now.
  • After recording the podcast, I decided I needed to look a little deeper at partial differential equations. I failed because I started reading Partial Differential Equations for Scientists and Engineers by Farlow. The presentation is very practical, not theoretical, so it doesn't address the problems in this podcast directly. However, the methods used in the text seem to directly contradict the general discussion in Tegmark (since every problem is both an initial value problem and a boundary value problem, simultaneously). I haven't worked my way through it, so maybe I'll change my mind, but not at present. I have fallen in love with the presentation. I think that if you'd like to learn to solve PDEs and have a sufficient background, this is the book for you (because this book makes me feel smart).

5. Please visit and comment on our subreddit, and if you can help us keep this going by contributing to our Patreon, we'd be grateful.

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Monday, October 29, 2018

The Einstein-Cartan Torsion Field Theory

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Recorded: 6/10/2018 Released: 10/29/2018

Randy explains some recent developments in the Einstein-Cartan torsion field to Jim. This theory introduces at least one tensor field representing the intrinsic angular momentum at a space-time point, and was originally intended to remove singularities from general relativity.
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Notes:

1. The papers we read for this program:

2. My review of Will's book. This paper serves as something of an update of it. A true update is scheduled to come in December 2018.

3. Related Episodes of Physics Frontiers:

4. Contact Randy at randy@physicsfm.com to take him up on his offer. Actually, I don't know if those e-mail redirects really work. I set them up some time ago, but I've never seen anything come in from them.

5. Please visit and comment on our subreddit, and if you can help us keep this going by contributing to our Patreon, we'd be grateful.

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Sunday, October 14, 2018

Metamaterial Stress Tensor

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Recorded: 5/26/2018 Released: 10/14/2018

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.
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Notes:

1. The papers we read for this program:

2. Our Patreon backers can see the Table of Stress Tensors I made for the podcast.

3. Other papers mentioned:

I found these papers useful for this program:

4. Books mentioned in this podcast:

  • J.D. Jackson's Classical Electromagnetism, 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.
  • Landau & Lifshitz' Electrodynamics of Continuous Media 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.
  • M. Schwartz' Principles of Electrodynamics (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.
  • U. Leonhardt and T. Philbin's Geometry and Light: The Science of Invisbility 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.
5. Related Shows:


8. Randy mentions Harry Reid's Advanced Aerospace Threat Identification Program (AATIP) program, a government UFO program funded from 2007 to 2014. It was run by Luis Elizondo, who Randy mentions in the podcast. Randy says he was directed to this topic by a discussion that Joe Rogan had with Thomas DeLonge who funds AATIP's private successor, To the Stars Academy. Although they focused on things that were out in left field (Harry Reid says he met his wife on a UFO, but no one believed him), you can see from this list that they funded some good research as well (such as Ulf Leonhardt's (see above) and Maxim Tsoi's in spintronics). I didn't count, but it looked to be about a sixth solid research, a sixth reasonable research, as sixth fringy stuff, and a half to EarthTech International.

7. Please visit and comment on our subreddit, and if you can help us keep this going by contributing to our Patreon, we'd be grateful.

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Friday, September 21, 2018

The String Theory Landscape

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Recorded: 5/12/2018 Released: 9/21/2018

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.

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Notes:

1. The papers we read for this program:
  • Susskind, L., "The Anthropic Landscape of String Theory" in Carr, Bernard (ed.), Universe or Multiverse? (Cambridge, 2009), 247-266. [arXiv]
  • Susskind, L., "Supersymmetry Breaking in the Anthropic Landscape" in Shifman, Vainshtein, and Wheater (eds.) From Fields to Strings: Circumnavigating Theoretical Physics (World Scientific, 2005). 1745-1749. [arXiv]
2. Books mentioned in this podcast:

3. Previous shows mentioned in this podcast:.



4. Related Shows:

5. Please visit and comment on our subreddit, and if you can help us keep this going by contributing to our Patreon, we'd be grateful.

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Friday, August 10, 2018

CPT Symmetry and Gravitation

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Recorded: 3/28/2018 Released: 8/10/2018

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.

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Notes:

1. The papers we read for this program:
2. I found these papers in the footnotes to Alberto Vecchiato's Variational Approach to Gravity Field Theories.

3. Please visit and comment on our subreddit, and if you can help us keep this going by contributing to our Patreon, we'd be grateful.

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Wednesday, July 25, 2018

Retrocausality

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Recorded: 3/3/2018 Released: 7/25/2018

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.

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Notes:

1. The papers we read for this program:
2. Books discussed in the program:


3. Huw Price also wrote a book about the philosophy of time called Time's Arrow and Archimedes' Point that, according to the plane ticket I was using as a bookmark, I last read in 2003.

4. A popular book I recently read on the de Broglie-Bohm interpretation and endorsing non-locality is Jean Bricmont's Quantum Sense and Nonsense.

5. Please visit and comment on our subreddit, and if you can help us keep this going by contributing to our Patreon, we'd be grateful.

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