Neil Turok: A Route to Quantum Gravity (Without Strings)
6/22/20261 hr 55 min
SPONSORS: - Go to https://www.plaud.ai/curt and use the promo code "CURT" to get a Plaud device today - Accelerate your efficiency. Sign up for your one-dollar-per-month trial today at http://shopify.com/theories - I personally subscribe to The Economist. TOE listeners get 35% off the annual subscription. No other podcast has this! https://economist.com/TOE This is a breaking podcast. We're premiering a new paradigm for quantizing 4D gravity here first, without strings. Neil Turok — inaugural Higgs Chair at Edinburgh, former director of Perimeter Institute, and 2026 Fellow of the Royal Society — believes quantum gravity may not require strings, extra dimensions, or a multiverse. The key: a 1970s theory called quadratic gravity, long abandoned over two seemingly fatal problems. Turok and Bateman argue both problems dissolve — one by reinterpreting a classical instability as ordinary gravitational expansion, the other by a subtle tweak to the Born rule that allows quantum states of negative norm without ever producing negative probabilities. One quiet assumption, Turok argues, underpins decades of string theory's necessity. Drop it, and the whole case for a multiverse unravels. Neil graciously gave me a sneak peek at his and his PhD student Sam Bateman's new research. Bleeding edge! I hope you enjoy. TIMESTAMPS: - 00:00:00 - Quadratic Gravity Emergence - 00:05:03 - Renormalization and Asymptotic Freedom - 00:10:57 - Ghosts and Krein Spaces - 00:16:00 - Generalizing the Born Rule - 00:23:27 - Ostrogradsky Instability Reinterpreted - 00:31:29 - UV Completeness and QCD - 00:38:21 - Higgs Compositeness and Hierarchy - 00:43:58 - CPT Symmetric Universe Minimalism - 00:52:54 - The 36 Fields Mystery - 01:00:10 - Orthodoxy vs. Revolutionary Ideas - 01:06:39 - Gravitational Entropy and Smoothness - 01:16:14 - Multiverse Measure Problem - 01:23:05 - Theoretical Physics Health - 01:30:07 - Sam Bateman’s Breakthrough - 01:43:33 - Philosophy of Cosmology LINKS MENTIONED: - Neil's Papers: https://inspirehep.net/authors/985402 - Renormalization of Higher-Derivative Quantum Gravity [Paper]: https://journals.aps.org/prd/abstract/10.1103/PhysRevD.16.953 - Quadratic Gravity: https://en.wikipedia.org/wiki/Quadratic\_gravity - Asymptotic Freedom in Higher-Derivative Quantum Gravity [Paper]: https://www.sciencedirect.com/science/article/abs/pii/0370269385902485 - Ostrogradsky's Theorem: http://www.scholarpedia.org/article/Ostrogradsky's\_theorem\_on\_Hamiltonian\_instability - Krein Space: https://en.wikipedia.org/wiki/Indefinite\_inner\_product\_space - CPT-Symmetric Universe [Paper]: https://arxiv.org/abs/1803.08928 - Pathologies of Dimension-Zero Scalar Fields [Paper]: https://arxiv.org/abs/2603.05683 - No-Ghost Theorem for Pais-Uhlenbeck Oscillator [Paper]: https://arxiv.org/abs/0706.0207 - Cancelling the Vacuum Energy [Paper]: https://arxiv.org/abs/2110.06258 - Gravitational Entropy [Paper]: https://arxiv.org/abs/2201.07279 - Neil's Lecture: https://pirsa.org/15100070 - Neil Turok on the Big Bang [TOE]: https://youtu.be/ZUp9x44N3uE - Neil Turok on Black Holes [TOE]: https://youtu.be/zNZCa1pVE20 - Carlo Rovelli [TOE]: https://youtu.be/hF4SAketEHY - Leonard Susskind [TOE]: https://youtu.be/2p\_Hlm6aCok - Jacob Barandes [TOE]: https://youtu.be/wrUvtqr4wOs - Geoffrey Hinton [TOE]: https://youtu.be/b\_DUft-BdIE - Harvey Friedman [TOE]: https://youtu.be/gx3uKT1qJvY - Scott Aaronson [TOE]: https://youtu.be/1ZpGCQoL2Rk - David Deutsch [TOE]: https://youtu.be/vKeWv-cdWkM - Peter Woit & Joseph Conlon [TOE]: https://youtu.be/fAaXk\_WoQqQ More links at https://curtjaimungal.substack.com FOLLOW: - Spotify: https://open.spotify.com/show/4gL14b92xAErofYQA7bU4e - Substack: https://curtjaimungal.substack.com/subscribe - Twitter: https://twitter.com/TOEwithCurt - Discord Invite: https://discord.com/invite/kBcnfNVwqs - Crypto: https://nowpayments.io/donation/TOE - PayPal: https://www.paypal.com/donate?hosted\_button\_id=XUBHNMFXUX5S4 Guests do not pay to appear. #science
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Transcript preview
First 90 secondsNeil Turok· Guest0:00
What happened at the Big Bang? What goes on in black holes? These kind of questions have not been solved by these very complex frameworks for quantum gravity.
Curt Jaimungal· Host0:09
You don't believe this, and you have some recent results.
Neil Turok· Guest0:13
I used to believe it, that quantizing gravity required extra dimensions, strings, membranes.
Curt Jaimungal· Host0:19
What are the assumptions that go into this theory?
Neil Turok· Guest0:21
One of them is that the theory lives in a Hilbert space. We have an example of a theory which doesn't require that assumption.
Curt Jaimungal· Host0:29
For some background- Yeah ... for the viewers, I was sent this paper last night. Professor Neil Turok is the inaugural Higgs chair at Edinburgh, former director of Perimeter, and a two thousand and twenty-six fellow of the Royal Society.
Neil Turok· Guest0:42
States of negative norm are called ghosts. A state with negative norm corresponds to a negative probability. That's just not true. You can't observe the norm of a quantum state. Provided the S-matrix or Hamiltonian of this theory has this symmetry, the answers you get are always positive, and the probabilities always add up to one. We claim we understand quantum gravity in a certain limit. The trick we used to make sense of it may or may not apply to the full thing.
Curt Jaimungal· Host1:14
On this channel, I, Curt Jaimungal, interview researchers regarding their theories of reality with rigor and technical depth.
Neil Turok· Guest1:21
Sam says, "I think I know how it works." And all it took is a slight tweak of the Born rule.
Curt Jaimungal· Host1:27
Today, ghosts, the Born