Friday, August 16, 2019

Loop Quantum Gravity

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Recorded: 6/13/2019 Released: 8/16/2019

Randy and Jim explore loop quantum gravity. Loop quantum gravity is a theory of space-time that emphasizes the random, pre-metric connections between points of a reasonably small size (the surface areas are on the order of the square of the Planck length) and the uncertainties therein.
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Notes:

1. The papers we read for this program:

2. Related Episodes of Physics Frontiers:


4. Carlo Rovelli has a very readable, and so far not too technical, introductory book on Loop Quantum Gravity, cleverly entitled Covariant Loop Quantum Gravity: an elementary introduction to quantum gravity and spinfoam theory. I think this is a pdf, if you want him to continue to live his monkish lifestyle.

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, July 15, 2019

Spooky Action at a Distance

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Recorded: 5/2/2019 Released: 7/15/2019

Randy and Jim discuss the lower bound on the speed of communication within a wave function, and the limits associated with it.
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Notes:

1. The papers we read for this program:

2. Related Episodes of Physics Frontiers:


3. Related Episodes of PhysicsFM: Quantum Paradoxes:



4. The experiments in this podcast were based on Bell's Theorem, and if you're unfamiliar with it, you should check out The Speakable and Unspeakable in Quantum Mechanics, a collection of Bell's essays, which I review here. I also have discussions of The Wave Function and Quantum Sense and Nonsense, the first a philosophical and the second an advanced non-technical account of the same phenomena.

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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Thursday, June 6, 2019

The Positive Energy Theorem

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Recorded: 12/9/2017 Released: 6/6/2019

Randy introduces a theory that purports to allow negative mass to Jim. It has been thought for quite a long time that negative mass was incompatible with general relativity, because it is possible to show that negative mass solutions are impossible. However Paranjape and his students noticed the proofs of this all relied on a flat background (zero cosmological constant). When trying to extend the theorems to a space with a negative cosmological constant, they found instead that negative mass is not prohibited.
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Notes:

1. The papers we read for this program:

2. Additional related paper for the positive energy theorem.:
3. Related Episodes of Physics Frontiers:



4. Details about just how well general relativity works can be found in Wills' Theory and Experiment in Gravitational Physics, whose work we reference in the podcast.

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, May 3, 2019

Entropic Gravity

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Recorded: 4/4/2019 Released: 5/3/2019

Randy and Jim discuss Eric Verlinde's theory of emergent gravity that relies on statistical methods to produce both gravitational attraction and inertial effects.
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Notes:

1. The papers we read for this program:

2. Additional related paper I half-read and we discussed:
3. Related Episodes of Physics Frontiers:



4. 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, February 24, 2019

The Chameleon Field

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Recorded: 11/3/2019 Released: 2/24/2019

Randy and Jim discuss the chameleon field - scalar field that mimics the effects of dark energy.
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Notes:

1. The papers we read for this program:

2. Related Episodes of Physics Frontiers:
  • Coming Soon



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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Sunday, December 23, 2018

The Octonions

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Recorded: 10/20/2018 Released: 12/23/2018

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.
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Notes:

1. The papers we read for this program:

2. Related Papers:

3. Related Episodes of Physics Frontiers:



4. Books mentioned in this podcast:

5. John Baez' webpage for all things octonion.

6. Cohl Furey's video series on the octonions and the standard model.

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, 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 psychic 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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