Emergent Gravity IV - Learning & Questions

[atyy]

So, in simple language since I don't know much about XGW's work, what do you conclude?

To me (knowing very little about it) it sounds from what you say as if there still could be some similarities between Wen-Gu and Markopoulou pictures.
An interesting aspect of her schema, that I have seen coming up repeatedly, is "disordered locality" which sounds like it might have something to do with "longrange entanglement".

I don't know. Wen's current picture is that there are many types of "long-range entanglement" of which Levin and Wen "string net condensation" is a type, while the Gu and Wen models seem to be "long-range entanglement" of a different type. However, he doesn't really understand long-range entanglement yet - ie. exactly how to distinguish between states with long-range entanglement and states without, or between different types of long-range entanglement.

Konopka, Markopoulou and Severini state that their quantum graphity model of "disordered locality" is related to Levin and Wen's "string net condensation" - if so, I presume that although quantum graphity appears related to "long range entanglement" of the "string net" sort, it is currently unknown whether it is related to other types of "long range entanglement" such as that apparently in the Gu and Wen model.

One partial tool that people have at the moment for studying "long range entanglement" is the "topological entropy". There seems to be a lot of interesting current work about this in condensed matter and quantum computing.

 

[John86]

http://arxiv.org/abs/0909.1044
Osmotic pressure of matter and vacuum energy
Authors: G.E. Volovik
(Submitted on 5 Sep 2009)
Abstract: The walls of the box which contains matter represent a membrane that allows the relativistic quantum vacuum to pass but not matter. That is why the pressure of matter in the box may be considered as the analog of the osmotic pressure. However, we demonstrate that the osmotic pressure of matter is modified due to interaction of matter with vacuum. This interaction induces the nonzero negative vacuum pressure inside the box, as a result the measured osmotic pressure becomes smaller than the matter pressure. As distinct from the Casimir effect, this induced vacuum pressure is the bulk effect and does not depend on the size of the box. This effect dominates in the thermodynamic limit of the infinite volume of the box. Analog of this effect has been observed in the dilute solution of 3He in liquid 4He, where the superfluid 4He plays the role of the non-relativistic quantum vacuum, and 3He atoms play the role of matter.

 

[John86]

http://arxiv.org/abs/0909.0160
Lorentz violation and black-hole thermodynamics: Compton scattering process
Authors: E. Kant, F.R. Klinkhamer, M. Schreck
(Submitted on 1 Sep 2009 (v1), last revised 7 Sep 2009 (this version, v2))
Abstract: A Lorentz-noninvariant modification of quantum electrodynamics is considered, which has photons described by the nonbirefringent sector of modified Maxwell theory and electrons described by the standard Dirac theory. These photons and electrons are taken to propagate and interact in a Schwarzschild spacetime background. For appropriate Lorentz-violating parameters, the photons have an effective horizon lying outside the Schwarzschild horizon. A particular type of Compton scattering event, taking place between these two horizons (in the photonic ergoregion) and ultimately decreasing the mass of the black hole, is found to have a nonzero probability. These events perhaps allow for a violation of the generalized second law of thermodynamics in the Lorentz-noninvariant theory considered.