Neil Turok: A Route to Quantum Gravity (Without Strings)

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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

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