 Speaker:

Stefan Zohren

Title: 
Taming the cosmological constant in 2D causal quantum gravity with
topology change 
Abstract: 
As shown in previous work, there is a welldefined nonperturbative
gravitational path integral including an explicit sum over topologies in
the setting of Causal Dynamical Triangulations in two dimensions. In this
paper we derive a complete analytical solution of the quantum continuum
dynamics of this model, obtained uniquely by means of a doublescaling
limit. We show that the presence of infinitesimal wormholes leads to a
decrease in the effective cosmological constant, reminiscent of the
suppression mechanism considered by Coleman and others in the
fourdimensional Euclidean path integral. Remarkably, in the continuum
limit we obtain a finite spacetime density of microscopic wormholes without
assuming fundamental discreteness. This shows that one can in principle
make sense of a gravitational path integral which includes a sum over
topologies, provided suitable causality restrictions are imposed on the
path integral histories.

Talk: 
Transparencies, Recorded Talk

 