Maxwellian Ratchets with Alex Jurgens

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Recorded: 2023/12/18 Released: 2024/03/31

Jim talks with Alex Jurgens of INRIA about Maxwellian Ratchets. These are abstract machines that react to outside stimuli, These are highly specified theoretical realizations of Maxwell's Demon, who flaunts the second law of thermodynamics. Jurgens discusses these in terms of entropy, information processessing, and the second law.
------------------------------------------- Notes:

1. The article that we discussed in this program:

• Kiefer, Claus, "Functional Thermodynamics of Mawellian Ratchets: Constructing and Deconstructing Patterns, Randomizing and Derandomizing Behaviors." Phys. Rev. Research 2 033334 (2020) [arXiv]

2. Related Episodes of Physics Frontiers:

• Physics Frontiers 74: Maxwellian Ratchets with David Wolpert
• Physics Frontiers 68: Qunatum Resource Theories with Gilad Gour

3. Books mentioned:

• The Road to Maxwell's Demon, Meir Hemmo and Orly R. Shenker. Claus' book on quantum gravity.
4. 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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Undecidability and Theories of Everything with Claus Kiefer

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Recorded: 2023/08/07 Released: 2024/01/28

Jim talks with Claus Kiefer about his recent essay on the relationship between the Gödel's incompleteness theoerems and the possibility of developing a theory of everything. Incompleteness was originally developed to show that every axiomatic system that is sufficiently robust admits well-formed statements that have a liar's paradox-like structure - if you assume the statement is true, you can prove it's false, and vice-versa. This statement is then said to be undecidable. Undecidability also famously comes up in the halting problem of computer science and the continuum hypothesis. Professor Kiefer speculates here that theories of everything are similarly undecidable.
------------------------------------------- Notes:

1. The article that we discussed in this program:

• Kiefer, Claus, "Gödel's undecidability theorems and the search for a theory of everything" (2023) [arXiv]

2. Other papers referred to in this podcast:

• Cubitt, T.,D. Perez-Garcia and H.M. Wolf, "Undecidability of the Spectral Gap." Nature 528 207 (2015) [arXiv]
• Goedel,, K., "On Formally Undecidable Propositions of Principia Mathematica and Related Systems." Monatshefte für Mathematik und Physik 38 173 (1931) [Free]
• The Undecidable [Amazon], M. Davis, ed. Reprints Goedel's paper and other work from the 1930's. Dover book.

3. Related Episodes of Physics Frontiers:

• Physics Frontiers 69: The Flavor Puzzle with Joe Davighi
• Physics Frontiers 62: Deformed Special Relativity
• Physics Frontiers 45: Loop Quantum Gravity
• Physics Frontiers 35: The String THeory Landscape.

4. Books mentioned:

• Quantum Gravity, 3rd. Ed., Claus Kiefer. Claus' book on quantum gravity.
• The Physical Basis of the Direction of Time, H. Dieter Zeh. Excellent book going over how the arrow of time might be directed via different aspects of physics. Video Review
• The Undecidable [Amazon], M. Davis, ed. Reprints Goedel's paper and other work from the 1930's. Dover book.
• The Character of Physical Law, Richard Feynman
• Road to Reality, Roger Penrose
• Non Standard Analysis, Abraham Robinson or Applied Non-Standard Analysis, Martin Davis. Two books on non-standard analysis. Despite The Undecidable and Applied Non-Standard Analysis being about 6" from each other on my bookshelves for at least a decade, I didn't make the connection that the editor of the first was also the author of the second until this moment.
• Goedel, Escher, Bach, D. Hofstadter.

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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The Measurement Problem with Nick Ormrod and V. Vilasini

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Recorded: 2023/07/17 Released: 2023/08/20

Jim talks with Nick Ormrod and V. Vilasini about their use of categorical probability theory to study the measurement problem of quantum mechanics. They use the CPT to analyze a no-go theorem to see where there are weaknesses in the underlying structure of quantum mechanics without referring to particular mathematical formualtions of the subject, allowing them to show that the measurement problem comes from difficulties in our understanding of the evolution of quantum states or the way we interpret measurements.
------------------------------------------- Notes:

1. The article that we discussed in this program:

• Ormrod, N., V. Vilasini, and J. Barrett, "Which Theories Have a Measurement Problem?" (2023) [arXiv]

2. Other papers referred to in this podcast:

• N. Ormrod and J. Barrett, "A No-Go Theorem for Absolute Observed Events Without Inequalities or Modal Logic." [arXiv]
• V. Vilasini and M. P. Woods, "A General Framework for Consistent Logical Reasoning in Wigner's Friend Scenarios: Subjective Perspectives of Agents Within a Single Quantum Circuit." [arXiv]
• Maudlin, T., "Three Measurement Problems." Topoi 14 7 (1995).

3. Related Episodes of Physics Frontiers:

• Physics Frontiers 46: Wigner's Friend
• Physics Frontiers 44: Spooky Action at a Distance
• Physics Frontiers 30: The Consistent Histories Interpretation of Quantum Mechanics
• Physics Frontiers 2: The de Broglie-Bohm Interpretation of Quantum Mechanics

4. 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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Stochastic Thermodynamics with David Wolpert

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Recorded: 2023/05/10 Released: 2023/07/09

Jim talks with David Wolpert about the stochastic thermodynamics of compuation. The discussion focuses on recent developments in the relationship between non-equilibrium processes and information processing, having deep implications on how we view the world and how we apply statistical physics to biological, computational, and other systems.
------------------------------------------- Notes:

1. The articles that we discussed in this program:

• Tasmin, F., N. Fuentes, and D. Wolpert, "The Fundamental Thermodynamic Costs of Communications." (2023) [arXiv]
• Wolpert, D., "Minimal Entropy Production of Interacting Systems." New Journal of Physics 22 113013 (2020) [arXiv]
• Wolpert, D., "The Stochastic Thermodynamcis of Computation." J. Phys. A: Math. Theor. 52 193001 (2019). [arXiv] (Review Article)

2. Other papers referred to in this podcast:

• Landauer, R., "Irreversibility and the Heat Generation in the Computing Process" (IEEE Reprint). IBM J. Res. Dev. 5 283 (1961).[Free] [see 4]
• Bennett, C.H., "Logical Reversibility of Computation." IBM J. Res. Dev. 17 525 (1973). [Free] [see 4]
• Sagawa, T., "Thermodynamic and Logical Reversibilities Revisited." J. Stat. Mech. 2014 P03025 (2014).[arXiv]
• Parrondo, J.M.R/, J. M. Horowitz, and T. Sagawa, "Thermodynamics of Information." Nature Physics 11, 131 (2015).
3. Related Episodes of Physics Frontiers:

• Physics Frontiers 68: Quantum Resource Theories
• Physics Frontiers 16: Stochastic Resonance Energy Harvesting
4. Many of the classic works about the thermodyanmics of information, including many by Landauer and Bennett who are discussed in the episodde, are reprinted in Maxwell's Demon [Amazon], edited by Leff and Rex. Supplementing this with some of the references above would be useful. 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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Quantum Money with Jiahui Liu

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Recorded: 2023/03/28 Released: 2023/06/18

Jim talks with Jiahui Liu about quantum money. Quantum Money is a key milestone in quantum crytography -- not for the breaking of codes (e.g., Shor's algothrithm), but instead for using quantum computing to improve cryptography beyond what is possible in classical cryptography. The difficulty is, however, a fully satisfactory way to implement quantum money is not currently known. Jiahui discusses both how to show that a possible implementation doesn't work, and how she developed another scheme to implemet quantum money. She also discusses the history of quantum money and some of the things quantum crytographers can do once they have a reliable quantum money scheme.
------------------------------------------- Notes:

1. The articles that we discussed in this program:

• Liu, J., H. Montogomery, and M. Zhandry, "Another Round of Breaking and Making Quantum Money: How to Not Build It from Lattices, and More." in Advances in Cryptography - EUROCRYPT2023 Lecture Notes in Computer Science 14004 611 (2023) [arXiv]

2. Related Episodes of Physics Frontiers:

• Physics Frontiers 64: The Born Rule

3. 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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The Born Rule and Gravity with Antony Valentini

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Recorded: 2023/03/03 Released: 2023/04/23

Jim talks with Antony Valentini about the status of the Born Rule in quantum gravity. In particular, it doesn't work. Since the wavefunction cannot be normalized in quantum gravity, there is no way to interpret Ψ as the knowledge of the observer about the quantum system. Instead, some realist interpretation of the wavefunction is required. In this regard, Jim and Anotony also discuss the de Broglie-Bohm interpretation in light of quantum gravity.
------------------------------------------- Notes:

1. The articles that we discussed in this program:

• Valentini, A., "Beyond the Born Rule in Qunatum Gravity." Found. Phys. 53, 6 (2023) [arXiv]
• Valentini, A., "Beyond the Quantum." Physics World 22, 32 (2009) [arXiv]

2. Some other articles mentioned in the podcast:

• Valentini, A., "Quantum Gravity and Quantum Probability." (2021) [arXiv]
• Kiefer, C. and T. Singh, "Quantum Gravitational Ccorrections to the Functional Schrödinger Equation." Phys. Rev. D 44 1067 (1991).
• Kiefer, C. and P. Peter, "Time in Quantum Cosmology." Universe 8 36 (2022). [arXiv].
• Bohm, D. "A Suggested Interpretation of Quantum Theory in Terms of 'Hidden' Variables I." Phys. Rev. 85, 166 (1952).
• Bohm, D. "A Suggested Interpretation of Quantum Theory in Terms of 'Hidden' Variables II." Phys. Rev. 85, 180 (1952).

3. Books mentioned in the podcast:

• Holland, P. R., The Quantum Theory of Motion: an Account of the de Broglie-Bohm Causal Interpretation of Quantum Mechanics. Cambridge, 1993. [Amazon]
• Anderson, E., The Problem of Time: Quantum Mechanics Versus General Relativity. Springer, 2017. [Amazon]

4. Antony's lectures mentioned in the discussion:

• Valentini, A., "The Born Rule Unstable in Quantum Gravity." Perimeter Institute, February 15th, 2018.>
• Valentini, A., "Quantum Gravity and Quantum Probability." Quantum Limits of Knowledge Conference, 2021.

5. Related Episodes of Physics Frontiers:

• Physics Frontiers 71: The Primordial Graviton Background
• Physics Frontiers 64: Teh Born Rule
• Physics Frontiers 51: Gravitational Wave Astronomy
• Physics Frontiers 2: The de Broglie-Bohm Interpretation of Quantum Mechanics

6. 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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The Primordial Graviton Background with Sunny Vagnozzi

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Recorded: 2022/12/01 Released: 2023/2/19

Jim talks with Sunny Vagnozzi of the University of Trento about a way to disprove inflationary theories of cosmology. All of them. If we were able to see a Primordial Graviton Background, which is the graviational equivalent to the cosmic microwave background, then we would know that there was no inflation. The event that would create the graviton background would have to occur before cosmic inflation started, and inflation would smooth it out. And the background would disappear.
------------------------------------------- Notes:

1. The article that we discussed in this program:

• Vagnozzi, S. and A. Loeb, "The Challenge of Ruling Out Inflation via the Primordial Graviton Background." ApJL 939, L22 (2022) [arXiv]

2. Related Episodes of Physics Frontiers:

• Physics Frontiers 59: The Hubble Crisis
• Physics Frontiers 57: Quantum Effects in Gravitational Waves
• Physics Frontiers 51: Gravitational Wave Astronomy
• Physics Frontiers 48: The Gertsenstein Effect

3. 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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