Pixelated Space Time with Philip Tee

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Recorded: 2024/12/19 Released: 2025/02/09

Jim talks with Philip Tee about the effects of having a pixelated space time. Phil uses doubly special relativity and quantum feild theory to explore models for spacetimes that are fundmentally discrete. Here he looks for tangible results in light bending and the Casimir effect.
------------------------------------------- Notes:

1. The articles that we discussed for this program:

• Davies, P.C.W. and P. Tee, "The Quantum Vacuum of Spacetime with a Fundamental Length." Phys. Rev. D 110 025009 (2024) [arXiv]
• Tee, P. and N. Jafari, "Fundamental length scale and the bending of light in a gravitational field." Eur. Phys. J. C 82, 571 (2022) [ arXiv ]

2. Related Episodes of Physics Frontiers:

• Physics Frontiers 72: Born's Rule and Qunatum Gravity with Antony Valentini
• Physics Frontiers 62: Deformed Special Relativity
• Physics Frontiers 45: Loop Qunatum Gravity
• Physics Frontiers 28: Quantum Vacuum the Casimir Effect
• Physics Frontiers 8: Vacuum Fluctuations and the Casimir Effect

3. Books mentioned in this podcast:

• Rovellio, C. and F. Vidotto, Covariant Loop Quantum Gravity, [Amazon] Cambridge (2022). This is the book I was referring to in the podcast.
• Gradshteyn, I.S. and I.M. Ryzhik Tables of Integrals, Series, and Products.[Amazon] I bought my copy used thirty-five years ago. I constantly used it, but now I almost always use Wolfram Alpha.

5. Please visit and comment on our subreddit, YouTube Channel, or Twitter account. These are also places to look for announcements of new episodes and the like. And if you could help us keep this going by contributing to our Patreon, we'd be grateful.

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Deformed Special Relativity

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Recorded: 2021/08/08 Released: 2022/02/13

Randy and Jim discuss first order corrections to special relativity in light of quantum gravity: deformed special relativity. What should happen to space time if a minimum length scale is introduced to special relativity?
------------------------------------------- Notes:

1. Papers we both read for this program:

• Amelino-Camelia, G., L. Friedel, J. Kowalski-Gikman, and L. Smolin, "The Principle of Relative Locality." Phys Rev. D 84, 084010 (2011). [arXiv]
• Hossenfelder, S., "The Box Problem in Deformed Special Relativity." (2009) [arXiv]
• Smolin, L., "Classical Paradoxes of Locality and Their Resolution in Deformed Special Relativity." Gen Relativ Gravit, 3671 (2011) [arXiv]
• Hossenfelder, S., "Comments on Nonlocality in Deformed Special Relativity" Phys Rev D 95> 084034 (2010). [arXiv]

2. Other papers one or the other of us read:

• Hossenfelder, S. "Minimal Length Scale Scenarios for Quantum Gravity." Living Reviews in Relativity 16, 2 (2013) [arXiv]
• R. Schtzhold, W. G. Unruh, "Large-Scale Non-Locality in ”Doubly Special Relativity” with an Energy-Dependent Speed of Light." JETP Lett. 78, 431 (2003). [arXiv]

3. Related Episodes of Physics Frontiers:

• Physics Frontiers 57: Quantum Effects in Gravitational Waves
• Physics Frontiers 45: Loop Quantum Gravity
• Physics Frontiers 42: Entropic Gravity
• Physics Frontiers 38: Why is Space-Time Four Dimensional?
• Physics Frontiers 30:The Consistent Histories Interpretation of Quantum Mechanics

4. Randy's obituary and my Patreon post on his death. 5. Please visit and comment on our subreddit, YouTube Channel and if you can help us keep this going by contributing to our Patreon, we'd be grateful.

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Multiversality

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Recorded: 2020/06/25 Released: 2020/12/06

Jim and Randy discuss rationales for the existence of a multiverse, guided by quantum mechanics, string theory, and the anthropic principle.
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Notes:

1. The papers we read for this program:

• Hogan, C. "Why the Universe is Just So." Reviews of Modern Physics 72, ? (2000). [arXiv
• Wilczek, F., "Multiversality/" Class. Quantum Gravity 30 , (2013). [arXiv]
• Tegmark, M., A. Aguirre, M.J. Rees, and F. Wilczek, "Dimensionless Constants, Cosmoloty, and Other Dark Matters." Phys. Rev. D 73, 023505 (2006) [arXiv]

2. Related Episodes of Physics Frontiers:

• Physics Frontiers 35: The String Theory Landscape
• Physics Frontiers 30: The Consistent Histories Interpretation of Quantum Mechanics
• Physics Frontiers 29: Gravitational Alternatives to Dark Energy
• Physics Frontiers 23: Dark Energy
• Physics Frontiers 2: The de Brogilie-Bohm Interpretation of Quantum Mechanics

3. Randy mentioned Sabine Hossenfelder's video on String Theory.
4. Jim mentioned Ian Hacking's The Emergence of Probabilty [Amazon]. This is a very intersting book that discusses the development of probability, with many interesting factoids along the way. In fact, it was in reading this book that I got the idea for the quantum dice.
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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The Unruh Effect

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Recorded: 2019/10/31 Released: 2019/04/04

Randy and Jim about the perspectival nature of quanta, the Unruh effect, which says that for highly accelerated systems, additional particles and temperature will be seen.
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Notes:

1. The papers we read for this program:

• Crispino, L.C.B, A. Higuchi, and G.E.A. Matsas, "The Unruh Effect and It's Applications." Rev. Mod. Phys. 80, 787 (2008). [arXiv]
• Akhmedov, E.T. and D. Singleton, "On the physical meaning of the Unruh effect." JETP Letters 86, 615 (2008). [arXiv]

2. Popular articles discussed on the program:

• Ingrid Fadelli, "Testing Hawking radiation in laboratory black hole analogues." Phys.org (20019).

3. Related Episodes of Physics Frontiers:

• Physics Frontiers 31: The Parameterized Post-Newtonian Framework.
• Physics Frontiers 9: f(R) Theories of Gravity.

4. Books discussed on this podcast:

• Leonhardt, U. and Philbin, T., Geometry and Light: The Science of Invisibility (2010). This is a textbook on using the methods of general relativity in the behavior of light in nonlinear materials that I quite enjoyed when I read it. It starts off with an old favorite, variational principles, like Fermat's principle of least time, and passes through a short course on differential geometry, before mixing light and geometry with Maxwell's equations. After that, he discusses optical analogs of black holes, the optical Aharonov-Bohm effect, and other topics -- like "cloaking at a distance:" invisibility! It has full color illustrations, which helps with differential geometry, and better, it's a Dover book so its cheap! [Amazon].

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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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:

• Khoury, J. and A. Weltmann, " Chameleon Fields: Awaiting Surprises for Tests of Gravity in Space." Phys. Rev. Lett. 90, 171104 (2004). [arXiv]
• Khoury, J., "Chameleon Field Theories." Class. Quantum Grav. 30, 214004 (2013). [arXiv]
• Khoury, J., "Detecting Dark Energy in Orbit – the Cosmological Chameleon" Phys. Rev. D 70, 123518 (2004). [arXiv]

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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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:

• Furey, C., "Unified Theory of Ideals" Phys Rev D 86, 025024 (2012). [Free]
• Furey, C, "Three Generations, Two Unbroken Gauge Symmetries, and One Eight-Dimensional Algebra" Phys Lett B 785, 84 (2018). [Free] [Supplement]

2. Related Papers:

• Furey, C., "Standard Model Physics from an Algebra" PhD. Thesis.
• Baez, J., "The Octonions." Bull. Amer. Math. Soc. 39 145 (2002).
• The Quanta magazine article that got Randy interested.

3. Related Episodes of Physics Frontiers:

• Physics Frontiers 35: The String Theory Landscape
• Physics Frontiers 30: The Consistent Histories Interpretation of Quantum Mechanics

4. Books mentioned in this podcast:

• Crowe, Michael, A History of Vector Analysis. A little bit dry, but a third of the book is about Hamilton and the quaternions.
• Whitehead, A.N., Process and Reality. If you think you're smart, try this.
• Fano and Fano, Physics of Atoms and Molecules. Lots of perturbations. That's what I remember.

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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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:

• Tegmark, M., "On the Dimensionality of Spacetime" Class Qunatum Grav 14, L69 (2009). [arXiv]
• Freeman, I.M., "Why Is Space Three-Dimensional? based on W. Buechel, "Warum hat der Raum drei Dimensionen?"" Am J Phys 37, 1222 (1969).

2. Other papers mentioned in this program:

• Dorling, J., "The Dimensionality of Time" Am J Phys 38, 539 (1970).
• Randy mentioned that Ken Wharton was working on a review of retrocausal models, which doesn't seem to have come out yet, but he has a more recent paper, "A New Class of Retrocausal Models" [arXiv that came out in Entropy.

3. Related Episodes of Physics Frontiers:

• Physics Frontiers 35: The String Theory Landscape
• Physics Frontiers 33: Retrocausality
• Physics Frontiers 17: The 2T Physics of Itzhak Bars

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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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:

• I reviewed Cosmic Update some time ago.
• I also reviewed the previous volume, Extra Dimensions in Space and Time, which includes a nice explanation of Itzhak Bars' 2T theory.

3. Previous shows mentioned in this podcast:.

• Physics Frontiers 18:The 2T Physics of Itzhak Bars

4. Related Shows:

• Physics Frontiers 23: Dark Energy

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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The Quantum Vacuum and the Casimir Effect

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Recorded: 9/16/2017 Released: 4/24/2018

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

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Notes:

1. The papers we read for this program:

• Jaffe, R.L. "The Casimir Effect and the Quantum Vacuum." Phys Rev D 72, 021301(R) (2005). [arXiv]
• Nikolic, N., " Is Zero-point Energy Physical? A Toy Model for Casimir-like Effect." Ann Phys 383, 181 (2017). [arXiv

2. We discuss an earlier episode on the Casimir Effect and van der Waals forces repeatedly in this one.

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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The Origin of Inertia

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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:

• The Origin of Inertia , James Woodward (blog post, 1998)
• On the Origin of Inertia, Sciama, D. W., Monthly Notices of the Royal Astronomical Society 113, 34 (1953)
• Study on Inertia as a Gravity Induced Property of Mass, in an Infinite Hubble Expanding Universe,Jeroen van Engelshoven, Advances in Mathematical Physics 2013, 801574 (2013)
• On the Origin of Mass, Wilczek, F.

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

• https://www.physicsforums.com/threads/the-origin-of-inertia.440707/
• https://www.physicsforums.com/threads/origin-of-inertia.657760/
• 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/12297-james-f-woodward-s-book-making-starships-and-stargates-march-10-2014
• 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/

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. 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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The 2T Physics of Itzhak Bars

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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. 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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Vacuum Fluctuations and the Casimir Effect

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Recorded: 2016/12/10 Published: 2017/04/27

What are the latest theoretical and experimental developments with the Casimir effect, and are vacuum fluctuations physical, or simply a convenient model for calculating the effects of quantum noise in the fields of matter? On this episode of Physics Frontiers, we explore some of the surprising discoveries that physicists have made unraveling the strange dynamics of mechanical components so small that they can’t even be seen through an optical microscope. And along the way we consider some of the fundamental mysteries of quantum field theory, as applied physics enters the realm of nanotechnology…and approaches exotic new possibilities like quantum levitation.

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Notes:

(1) Materials Perspective on Casimir and van der Waals Interactions by Woods, et al., the basis for this discussion.

(2) Our Subreddit

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