Condensed matter approach to QG:

Mode decomposition of action, integrate out high energy modes, absorb changes into redefined parameters. If successful, find a fixed point for these transformations.

Can stop just at integrating out of high energy modes. This corresponds to EFT.

Relevant to condensed matter bc topological invariants play role both there and in relative locality considerations.

Relative locality: theory of QG must entail relativity of point-coincidences. b/c momentum obeys non-linear composition law a la non-linear SR law of velocity combination.

Asymptotic safety:

GR as QFT non-renormalizable. So might think non-fundamental effective theory.

But Weinberg thinks safety might allow it to be fundamental after all.

Question arises: what is fundamental theory,

Two questions: why guiding principles in qg.

empirical guidance is unavailable.

Why these two? Little on asymptotic safety and relative locality.

Two Principles of Quantum Gravity in the Condensed Matter Approach

This is restricted from 3 principles for the sake of time.

D.O.: Isn’t a boundary less fundamental than something that’s not a boundary?

EK: No. This is the container view again.

MS: Are you happy for both to be equally fundamental? Are all grades of fundamentally equivalent?

EK. Yes. [Rest of answer lost]

JB: In EM, holonomies are non-local and vastly overcomplete. Fundamental meaning sub-ontic? If we resist your view, it is in part that we believe that dimension is background for everything else we do in physics.

EK. But need to cash out why that is difficult. Prima facie, we can cope with indeterminate dimensionality.  Why must it be determinate? Doesn’t quantum gravity do away with the container view entirely?

NH: One of the things relevant to T duality is that both of the duals predict that the space is large. States in either dual have an interpretation in terms of dual processes.  It doesn’t matter which you choose. Is this similar to AdS/CFT? What would beings who live in either of these spaces experience?

KH: If we define things functionally/structurally then plausible that we only live in one.

DB: Suppose the correct theory of our world is dual to boundary CFT.  Say I ostend to dimensions, then I’ve fixed what I mean and the theory on the boundary is just a notational variant. 

EK: Any such theory will require us to identify my experiences within the theory. Are there principled reasons to prefer one description to the other?.

But what about fundamentality?  Can we use our previous criteria?

If equivalence is precise, hard to ground claims of superiority. But one could be more revealing w.r.t. structure of underlying [CW: Or overlying?] theory.  However, the usual claim is that duality implies equivalence.  The moral of this talk is that differences in dimensionality don’t need to have physical significance.

Distinguish between dimensionality of physical degrees of freedom and spacetime. Note that d.o.f. don’t disappear, they are just translated into a different form.

If we accept that we can have distinct representations of the same situation anyway then duality is less puzzling.

To the questions in good time!