Neil Turok
speaker
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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Appearances
in which the only degrees of freedom are the local scale of the metric.
So this is fine for describing cosmology.
Even there are black hole-like solutions to this theory.
It's a kind of toy model for quantum gravity.
The trick we used to make sense of it may or may not apply to the full thing.
We will have to search in the full theory, is there a similar discrete symmetry, this thing that gives plus one on positive norm minus one?
If there is, then this will be a complete theory of quantum gravity.
Well, let me first say what the assumptions were behind the claim that you need strings and 10 dimensions to do quantum gravity.
The assumptions underlying that claim were that...
essentially the only allowed theories had two derivatives in the action.
So when people quantize strings, they were not considering theories even of strings which had four derivatives.
So that was one assumption.
There are plenty of other assumptions.
Probably the most
the strongest assumption was that you have to construct the theory only in perturbation theory.
The thing that's always bothered me about string theory is it has no full formulation.
There's nothing like general relativity where there's a principle that gives you the full nonlinear theory.
String theory is kind of constructed with certain, trying to respect certain principles like Lorentz invariance and the unitarity, positive probabilities and so on.
But string theories, the assumptions were really rigid.
One of them is that the theory lives in a Hilbert space, which means that the norms of all quantum states are positive.
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