Thermodynamics/gravity/CFT correspondence

[Demystifier]

Some evidence (Bekenstein, Hawking, Jacobson, Verlinde, ...) points to the idea that gravity is really a thermodynamic theory in disguise. Other evidence (Susskind, Maldacena, Witten, ...) points to the idea that gravity is dual to a lower dimensional conformal field theory (CFT). Are these two ideas mutually compatible? Can they both be true, and does it mean that some CFT's are really thermodynamic theories in disguise?

 

[malawi_glenn]

Evidence?

Any particular papers?

 

[martinbn]

I don't know if they can both be true, but they can both be wrong.

 

[Demystifier]

Evidence?

Any particular papers?

https://inspirehep.net/literature/394001
https://inspirehep.net/literature/451647

 

[Vanadium 50]

"Evidence" to me is something you get in a lab. I am not sure we have that here.

 

[Demystifier]

"Evidence" to me is something you get in a lab. I am not sure we have that here.

Here I present experimental evidence that the word "evidence" is also used in theoretical high energy physics:
https://arxiv.org/search/hep-th?que...acts=show&order=-announced_date_first&size=50

 

[Vanadium 50]

Is that evidence? Or is it an observation?

Relativistic thermodynaics is troublesome. How does temperature transform? You get different answers depending on how you define it - equivalent formulations for non-relativistic thermodynamics give different answers when extended.

The field has pretty much finessed this by avoiding this - e.g. dealing only with the rest frame or observing (there, that word again) that we never have two objects at high relative speed interacting and being in equilibrium at the same time. So maybe it doesn't matter.

Gravity has its own issues - you can't sensibly quantize it, dark energy is poorly understood, and there are huge swaths of untested parameter space: the reason MOND hasn't been swatted like a bug is that you can't build a MOND-swatter in a lab.

So could there by a deep relationship between two poorly understood theories? I guess. Just not sure what good it does. Like the old joke about the Siamese-Swahili dictionary - if you know one language you can learn the other!

 

[ohwilleke]

Some evidence (Bekenstein, Hawking, Jacobson, Verlinde, ...) points to the idea that gravity is really a thermodynamic theory in disguise. Other evidence (Susskind, Maldacena, Witten, ...) points to the idea that gravity is dual to a lower dimensional conformal field theory (CFT). Are these two ideas mutually compatible? Can they both be true, and does it mean that some CFT's are really thermodynamic theories in disguise?

This seems amenable to reasonably straightforward theoretical analysis. I wonder if anyone's every written a paper on it.

Both thermodynamic theories and conformal field theories have well defined mathematical properties. There are equations that define thermodynamics at a very fundamental and universal level, and a conformal field theory is a field theory that preserve angles.

It isn't trivially obvious, however, if this is or is not true.

 

[mitchell porter]

https://arxiv.org/abs/1601.07558
What is the Entropy in Entropic Gravity?
Sean M. Carroll, Grant N. Remmen

We investigate theories in which gravity arises as a consequence of entropy. We distinguish between two approaches to this idea: holographic gravity, in which Einstein's equation arises from keeping entropy stationary in equilibrium under variations of the geometry and quantum state of a small region, and thermodynamic gravity, in which Einstein's equation emerges as a local equation of state from constraints on the area of a dynamical lightsheet in a fixed spacetime background. Examining holographic gravity, we argue that its underlying assumptions can be justified in part using recent results on the form of the modular energy in quantum field theory. For thermodynamic gravity, on the other hand, we find that it is difficult to formulate a self-consistent definition of the entropy, which represents an obstacle for this approach. This investigation points the way forward in understanding the connections between gravity and entanglement.