Jonathan Oppenheim: Why Gravity Might Not Be Quantum After All

Theories of Everything with Curt Jaimungal

Curt Jaimungal

Physics, Philosophy, Society & Culture, Science

4.6 • 606 Ratings

🗓️ 10 September 2024

⏱️ 67 minutes

🔗️ Recording | iTunes | RSS

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Summary

Jonathan Oppenheim (UCL) challenges quantum gravity orthodoxy, arguing spacetime remains fundamentally classical. He examines quantum‑classical hybrid dynamics, path integrals, and the role of observation in collapse, offering fresh perspectives on the foundations of physics.- 00:00 - Intro- 01:08 - Quantum Mechanics and Classical Mechanics- 06:05 - Quantizing Gravity- 10:30 - How Gravity is Different- 16:07 - Classical-Quantum Gravity- 21:42 - Quantum Mechanics- 25:23 - Example of Continuous Master-Equation- 28:45 - Observation Causes a Collapse- 35:20 - Path Integrals- 49:34 - Intuitions- 59:32 - Is Spacetime Classical?- 01:03:05 - Outro / Support TOESPONSORS:- I personally subscribe to The Economist. TOE listeners get 35% off the annual subscription. No other podcast has this! https://economist.com/TOE- Indeed: Get your jobs more visibility – https://indeed.com/theories ($75 credit to book your job visibility)- HelloFresh: FREE breakfast for life – https://www.HelloFresh.com/freetheoriesofeverythingRESOURCES:- Sean Carroll on TOE: https://www.youtube.com/watch?v=9AoRxtYZrZo- Jonathan's first appearance on TOE: https://www.youtube.com/watch?v=NKOd8imBa2s- Jonathan's paper on hybrid classical-quantum dynamics: https://arxiv.org/pdf/2203.01332- Jonathan's paper on a post-quantum theory of classical gravity: https://journals.aps.org/prx/pdf/10.1103/PhysRevX.13.041040- Jonathan's website: https://www.ucl.ac.uk/oppenheim/- List of all of Jonathan's published papers: https://arxiv.org/search/?query=Oppenheim%2C+Jonathan&searchtype=author&abstracts=show&order=-announced_date_first&size=50- Patreon: https://patreon.com/curtjaimungal (early access to ad-free audio episodes!)- Listen on Spotify: https://open.spotify.com/show/4gL14b92xAErofYQA7bU4e- Become a YouTube Member Here: https://www.youtube.com/channel/UCdWIQh9DGG6uhJk8eyIFl1w/join- Join TOEmail at https://www.curtjaimungal.org- Crypto: https://tinyurl.com/cryptoTOE- PayPal: https://tinyurl.com/paypalTOE- TOE Merch: https://tinyurl.com/TOEmerch- Instagram: https://www.instagram.com/theoriesofeverythingpod- TikTok: https://www.tiktok.com/@theoriesofeverything_- Twitter: https://twitter.com/TOEwithCurt- Discord Invite: https://discord.com/invite/kBcnfNVwqs- iTunes: https://podcasts.apple.com/ca/podcast/better-left-unsaid-with-curt-jaimungal/id1521758802- Pandora: https://pdora.co/33b9lfP- Subreddit r/TheoriesOfEverything: https://reddit.com/r/theoriesofeverything Theories of Everything with Curt Jaimungal features long-form, technically detailed interviews with leading researchers in physics, mathematics, consciousness, and philosophy, exploring topics at the level of active research. For academics, graduate students, and anyone seeking depth beyond popular science. FOLLOW: Substack | Spotify | YouTube | Twitter Learn more about your ad choices. Visit megaphone.fm/adchoices Learn more about your ad choices. Visit megaphone.fm/adchoices Learn more about your ad choices. Visit megaphone.fm/adchoices Learn more about your ad choices. Visit megaphone.fm/adchoices Learn more about your ad choices. Visit megaphone.fm/adchoices

Transcript

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0:00.0	I think it's reasonable to question whether we should be quantizing space time, like we've quantized all the gauge theories.
0:06.8	If it was classical, then it has a number of intriguing features like the measurement postulate is not needed.
0:13.1	It may help explain dark matter and dark energy.
0:18.5	Some ideas are so radical, they border on heresy.
0:24.0	Professor Jonathan Oppenheim, a distinguished theoretical physicist at University
0:28.6	College London, has proposed a theory that may just fit that bill.
0:33.2	His provocative framework suggests that gravity itself can remain classical in a quantum universe,
0:40.1	an idea that's riling up colleagues and undoing decades of theoretical physics gospel,
0:46.3	which asserts that gravity must be quantized.
0:49.4	Oppenheim directly refutes Feynman's arguments about the double-slid experiment
0:53.4	while showing how this
0:54.9	controversial approach could solve long-standing mysteries, not only with gravity, but also with the
1:00.5	measurement problem and the nature of dark energy and dark matter.
1:09.0	Okay, Professor, welcome. Take it away.
1:12.0	Great. So I'm going to be talking about the attempt to reconcile quantum mechanics and gravity or space time.
1:21.9	And this is joint work with a number of my students and Isaac Leighton, Muhammad Sajid, Barbara Soda, Andrea Rousseau,
1:30.0	Zach Wetter Davies, Andrew Guttka, etc. So it's joined project. We can start by asking just a more
1:36.4	simpler fundamental question, which is we have these two frameworks in physics. One is quantum
1:41.8	mechanics and the other one is classical mechanics. And we can just ask the question, are these two frameworks compatible? Can we combine them in a consistent mathematical way?
1:51.0	So quantum mechanics, we're used to the Heisenberg equation. We have a density matrix sigma, and it evolves as the commutator with the Hamiltonian.
2:03.3	And classical mechanics has a very similar form if we think of a probability
2:06.8	distribution row.
	...

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