Neil Turok

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2,693 appearances 2 recordings 1 series first heard Apr 2025 last heard 22 Jun

Neil Turok’s voice in public audio — every appearance, attributed to the second.

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Theories of Everything with Curt Jaimungal · Neil Turok: A Route to Quantum Gravity (Without Strings) · 22 Jun 2026 podcast

So they recapitulate.

various old arguments, one of which is Ostrogradsky.

They do something quite strange in their paper, which is the following, that these four derivative scalars of the type we introduced for cosmological reasons and to explain the micro background,

These four derivative theories are coupled to gravity, but the way we used them was to say, given a curved space background, given a spacetime, put these scalar fields on and see how they quantum fluctuate.

Klein and Held don't do that.

They put in the scalar fields, which couple to gravity, and they treat their action as if it is the gravitational action.

Okay, it's not.

Sorry, can you explain the difference between those two approaches?

Yeah, so in the one approach you treat, in the approach we used, because at that time we weren't yet ready to study quantum gravity, right?

So we said, okay, we'll do something simpler, which is to assume a curved background, but that's just fixed.

Then we studied quantum fields on that background.

Actually, the question we were asking is, what is the stress energy in quantum fields fluctuating on a fixed background?

The puzzle we wanted to resolve is, does that stress energy make sense?

You see, there's a terrible thing about quantum fields, even in a fixed background, their energy is infinite.

There's what's called a UV divergence.

We were trying to study gravity in two steps.

First of all, just take a curved background with fields on it.

Then take those fluctuations, calculate the energy in them, and see what effect those would have on the gravity.

It's not a full-blown theory.

It's just an attempt to understand how can gravity possibly couple to quantum fields that have divergent energy?

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