New aspects of two-dimensional quantum gravity

TL;DR

This paper explores two-dimensional quantum gravity using causal dynamical triangulations (CDT), revealing its connections to Euclidean quantum gravity, generalizations, and implications for the nature of time in quantum gravity.

Contribution

It introduces a generalized CDT model with string field theory and matrix model representations, and discusses its implications for understanding time as stochastic branching in quantum gravity.

Findings

CDT relates to Euclidean 2D quantum gravity.

Generalized CDT admits string field theory and matrix model forms.

Time may be viewed as stochastic branching into baby universes.

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.