Two New CDT Papers: AS Disc. & Stochastic Time

[John86]

How do these two papers fit in the hole AS discussion, or are they unrelated. Ambjörn and Loll visited the Asymptotic safety conference at PI in november !

http://arxiv.org/abs/0911.4211
Proper time is stochastic time in 2d quantum gravity
Authors: J. Ambjorn, R. Loll, Y. Watabiki, W. Westra, S. Zohren
(Submitted on 21 Nov 2009)
Abstract: We show that proper time, when defined in the quantum theory of 2d gravity, becomes identical to the stochastic time associated with the stochastic quantization of space. This observation was first made by Kawai and collaborators in the context of 2d Euclidean quantum gravity, but the relation is even simpler and more transparent in he context of 2d gravity formulated in the framework of CDT (causal dynamical triangulations).

http://arxiv.org/abs/0911.4208
New aspects of two-dimensional quantum gravity
Authors: J. Ambjorn, R. Loll, Y. Watabiki, W. Westra, S. Zohren
(Submitted on 21 Nov 2009)
Abstract: Causal dynamical triangulations (CDT) can be used as a regularization of quantum gravity. In two dimensions the theory can be solved anlytically, even before the cut-off is removed and one can study in detail how to take the continuum limit. We show how the CDT theory is related to Euclidean 2d quantum gravity (Liouville quantum gravity), how it can be generalized and how this generalized CDT model has a string field theory representation as well as a matrix model representationof a new kind, and finally how it examplifies the possibility that time in quantum gravity might be the stochastic time related to the branching of space into baby universes.

 

[marcus]

How do these two papers fit in the hole AS discussion, or are they unrelated...

The relation to the Asymptotic Safety QG program is described in the first paragraph of each paper---they put the AS relation up front, in the introduction.

In both papers, reference [1] is to Steven Weinberg's 1979 asymptotic safety proposal.

The two papers are quite similar, and much of the text is duplicated verbatim. However, the second paper "New Aspects" is much better edited. The first has random blunders of spelling and syntax. More care has gone into the preparation of the "New Aspects" version.

I think what happened is that the same talk was given both in June 2009 at Zakopane at a QG/QCD workshop and later in August at Capetown, for the George Ellis 70th Birthday Party---the "Ellis Fest". In both cases the proceedings are to be published. The Polish journal Acta Polonica will publish the talks given at Zakopane and the Cambridge University Press will make a kind of birthday book for George Ellis containing all the talks given at his 70th. He's a great guy and a lot of famous people gathered to celebrate and present talks. So it is absolutely necessary that there be two separate papers, one for Acta Polonica and one for Cambridge to publish.

However, for our purposes, it may be we only have to read and refer to one of them. I would pick "New Aspects", because I think it has slightly more in it and is easier to read. If anyone notices some essential content that is in the other paper and not in "New Aspects" please let us know!

 

[Entropia]

These two papers are related to the asymptotic safety (AS) discussion in the sense that they both address different aspects of two-dimensional quantum gravity, which is a topic that has been extensively studied in the context of AS. However, they are not directly related to the discussions that took place at the AS conference at PI in November.

The first paper, "Proper time is stochastic time in 2d quantum gravity", explores the connection between proper time and stochastic time in the framework of causal dynamical triangulations (CDT). This is a topic that has been previously studied by Kawai and collaborators in the context of 2d Euclidean quantum gravity, but the authors show that this relation is even simpler and more transparent in the context of 2d gravity formulated in CDT. This paper does not directly address the AS discussion, but it is relevant to the field of quantum gravity and provides insights into the nature of time in this context.

The second paper, "New aspects of two-dimensional quantum gravity", discusses various aspects of CDT as a regularization of quantum gravity in two dimensions. It also explores the connection between CDT and Euclidean 2d quantum gravity, and how the theory can be generalized and represented in different ways. The paper also suggests that time in quantum gravity might be related to the stochastic time associated with the branching of space into baby universes. While this paper does not directly address the AS discussion, it is relevant to the broader field of quantum gravity and provides new insights into the behavior of the theory.

In conclusion, these two papers are related to the AS discussion in the sense that they both address different aspects of two-dimensional quantum gravity, but they are not directly related to the discussions that took place at the AS conference at PI in November. They provide new insights into the nature of time in quantum gravity and contribute to the ongoing research in this field.