| Speaker:
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Stefan Zohren
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Title: |
Taming the cosmological constant in 2D causal quantum gravity with
topology change |
| Abstract: |
As shown in previous work, there is a well-defined 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 double-scaling
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
four-dimensional 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.
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| Talk: |
Transparencies, Recorded Talk
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