Dark Stars

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Recorded: 2021/06/10 Released: 2021/10/31

Randy and Jim discuss various proposals for objects that mimic black holes. Most of these are based on physics that disallows an infinitely dense point at the center of the black hole, such as string theory or loop quantum gravity, and some include very exotic matter.
------------------------------------------- Notes:

1. Papers we both read for this program:

• Nikitin, I., "On Dark Stars, Planck Cores, and the Nature of Dark Matter ." BLED Proc. 23rd Wkshp. 1, 221 (2021) [arXiv]
• Visser, M., C. Barcelo, S. Liberati, and S. Sonego, "ISmall, Dark and Heavy: But Is It a Black Hole?." PoS BHs, GRandStrings 2008, 105009 (2008) [arXiv]
• Holdom, B. and J. Ren, "Not Quite a Black Hole." Phys Rev D 95> 084034 (2017). [arXiv]

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

• Nikitin, I. "RDM-Stars and Galactic Rotation Curves." 2021 J. Phys. Conf. Series (2021) [arXiv]

3. Related Episodes of Physics Frontiers:

• Physics Frontiers 57: Quantum Effects in Gravitational Waves
• Physics Frontiers 51: Gracitational Wave Astronomy
• Physics Frontiers 45: Loop Quantum Gravity
• Physics Frontiers 25: Gravitational Field Propulsion
• Physics Frontiers 7: Virtual Gravitational Dipoles

4. 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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Warp Bubbles

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Recorded: 2021/03/25 Released: 2021/09/12

Randy tells Jim about solutions in general relativity that allow for isolated bubbles of spacetime that could, possibly, travel faster than light.
------------------------------------------- Notes:

1. Papers we both read for this program:

• Lobo, F.S.N. and M. Visser, "Fundamental Limitations on "Warp Drive" Spacetimes." Clas. Quant. Grav. 5871 21, (2004) [arXiv]
• Bobrick, A. and G. Maitre, "Introducing Physical Warp Drives." Clas. Quant. Grav. 38, 105009 (2021) [arXiv]

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

• Lentz, E. " Breaking the Warp Barrier: Hyper-Fast Solitons in Einstein-Maxwell-Plasma Theory ." Clas. Quant. Grav. 38 075015 (2021) [arXiv]
• Carmona, A., J.C. Ruiz, and, M. Neubert "A Warped Scalar Portal to Fermionic Dark Matter." Eur. Phys. J. C 81, 58 (2021) [arXiv]

3. Related Episodes of Physics Frontiers:

• Physics Frontiers 47: Bumetric Gravity
• Physics Frontiers 39: Negative Effective Mass
• Physics Frontiers 31: The Parameterized Post-Newtonian Framework
• Physics Frontiers 25: Gravitational Field Propulsion
• Physics Frontiers 7: Virtual Gravitational Dipoles

Physics Frontiers 6: General Relativity for the Experimentalist

4. 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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The Hubble Crisis

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Recorded: 2021/01/07 Released: 2021/07/05

Randy and Jim the differences between measurements in the Hubble constant and some proposals to resolve the issue.
------------------------------------------- Notes:

1. The papers we read for this program:

• Addison, G.E>, D.J. Watts, C.L. Bennett, M. Halpern, and G. Hinshaw, "Elucidating ΛCDM: Impact of Baryon Acoustic Oscillation Measurements on the Hubble Constant Discrepancy." ApJ 853, 119 (2018) [arXiv]
• Agrawal, P., F.-Y. Cyr-Racine, D. Pinner, L. Randall "Rock'n'Roll Solutions to the Hubble Tension." (2019) [arXiv]
• ..., "A Gravitational-wave Measurement of the Hubble Constant Following the Second Observing Run of Advanced LIGO and Virgo ." ApJ 909, 208 (2021). [arXiv]
• Carnegie Supernova Project, " The Carnegie Supernova Project: Absolute Calibration and the Hubble Constant ." ApJ 869 56 (2018) [arXiv]
• Yang, T. S. Birrer, and B. Hu, "The first simultaneous measurement of Hubble constant and post-Newtonian parameter from time-delay strong lensing." Mon. Notices Royal Astron. Soc. 497, L56 (2020) [arXiv]

2. Related Episodes of Physics Frontiers:

• Physics Frontiers 56: Multiversality
• Physics Frontiers 35: The String Theory Landscape
• Physics Frontiers 31: The Parameterized Post-Newtonian Framework
• Physics Frontiers 9: f(R) Theories of Gravity

3. Wendy Freedman recently published this article about the same topic, which some people say resolves the tension (It came out in the arXiv in June, we recorded in January, so it wasn't included). After going through it this weekend (7/17-18), I don't think it makes as strong a conclusion as the press made out, but it is worth reading, even at 48 pages. 4. 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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Phantom Matter

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Recorded: 2020/11/09 Released: 2021/06/06

Randy and Jim discuss a set of potential theories that could constitute dark matter that connect to normal matter through the Higgs particle.
------------------------------------------- Notes:

1. The papers we read for this program:

• Patt, B. and F. Wilczek, "Higgs-field Portal into Hidden Sectors." (2006). [arXiv
• Kanemura, S., S. Matsumoto, and N. Okada, "Can WIMP Dark Matter Overcome the Nightmare Scenario?" Phys. Rev. D 82, 055026 (2020) [arXiv]
• Lopez-Honorez, L., T. Schwetz, and J. Zupan "Higgs portal, fermionic dark matter, and a Standard Model like Higgs at 125 GeV." Phys. Lett. B 716, 179 (2012) [arXiv]
• CMS COllaboration "Search for charged Higgs bosons produced in vector boson fusion processes and decaying into vector boson pairs in proton-proton collisions at √s = 13 TeV." Phys. Lett. B 793, 520 (2020) [arXiv]

2. Related Episodes of Physics Frontiers:

• Physics Frontiers 52: Sterile Neutrinos
• Physics Frontiers 42: Entropic Gravity
• Physics Frontiers 9: f(R) Theories of Gravity

3. Jim recently appeared on Anthony Jeannot's Highbrow Drivel podcast, displaying his innate ability to talk out of his ass for 60 minutes. Check it out. 3. 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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Quantum Effects in Gravitational Waves

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Recorded: 2020/10/01 Released: 2021/05/02

Jim and Randy discuss two proposals for experiments that would be sensitive to a quantum particle of gravity. Unlike electromagnetism where the quanitzation of matter requires a photon field, the quantization of matter does not require quantized gravitons.
------------------------------------------- Notes:

1. The papers we read for this program:

• Guerreireo, T. "Quantum Effects oin Gravity Waves." Class. Quantum Grav. 37, 155001 (2020). [arXiv
• Parikh, M., F. Wilczek, and G. Zahariade, "The Noise of Gravitons." Int. J. Mod. Phys. D 29, 2042001 (2020) [arXiv]

2. Other papers mention in this podcast:

• Dyson, F. "Is a Graviton Detectable?." Int. J. Mod. Phys. A 28, 1330041 (2013). [pdf
• Feynman, R., "The Quantum Theory of Gravitation." Acta Phys.Polon. 24 (1963) 697-722 24, 697 (1963).

3. Related Episodes of Physics Frontiers:

• Physics Frontiers 51: Gravitational Wave Astronomy
• Physics Frontiers 48: Graviton-Photon Oscillations
• Physics Frontiers 45: Loop Quantum Gravity
• Physics Frontiers 43: Positive Energy Theorem

4. Randy mentioned our first podcast, Physics FM where we were discussing Aharonov and Rohrlich's Quantum Paradoxes.
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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Transcript (Rough Draft)
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The Anomalous Magnetic Moment of the Muon

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Recorded: 2020/07/23 Released: 2021/04/01

Jim and Randy discuss measurements of the anomalous magnetic moment of the muon, as well as what the discrepency between theory and experiment might mean as far as new physics.
------------------------------------------- Notes:

1. The papers we read for this program:

• Queiroz, F.S. and W. Shepherd "New Physics Contributions to the Muon Anomalous Magnetic Moment: A Numerical Code." Phys. Rev. D 89, 095024 (2014). [arXiv
• Davoudiasi, H. and W.J. Marciano, "A Tale of Two Anomalies." Phys. Rev. D 98, 075011 (2018). [arXiv]
• Blum, T., P.A. Boyle, T. Izubuchi, L. Jin, C. Jung, A. Juttner, C. Lehner, A. Portelli, and J.T. Tsang, "Calculation of the Hadronic Vacuum Polarization Contribution to the Muon Anomalous Magnetic Moment." Phys. Rev. Lett. 121, 022003 (2018) [arXiv]
• Fienberg, A.T., "The Status and Prospects of the Muon g − 2 Experiment at Fermilab." Contribution to the 2019 QCD session of the 54th Rencontres de Moriond (2019) [arXiv]

2. Related Episodes of Physics Frontiers:

• Physics Frontiers 54: The ANITA Experiment
• Physics Frontiers 52: Sterile Neutrinos
• Physics Frontiers 50: X17
• Physics Frontiers 30: Consistent Histories Interpretation of Qunatum Mechanics
• Physics Frontiers 14: Stochastic Electrodynamics

3. Fermilab's Muon g-2 Experiment.
4. The Mathematica Notebook mentioned in the first article. You can use this to explore different kinds of beyond the standartd model particles in the way the authors did.
5 Jim mentioned Melvin Schwartz's Principles of Electrodynamics [Amazon], an old textbook that goes into the details of the measurement of the anomalous magnetic moment. Because this is at least the second time I've used it extensively for the podcast, I have made a video, available here describing the book. Fortunately, my phone only had space for a 14 minute video, so I had to shut up about it.
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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Transcript (Rough Draft)
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