English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

The recent progress in the Causal Dynamical Triangulations (CDT) approach toquantum gravity indicates that gravitation is nonperturbatively renormalizable.We review some of the latest results in 1+1 and 3+1 dimensions with specialemphasis on the 1+1 model. In particular we discuss a nonperturbativeimplementation of the sum over topologies in the gravitational path integral in1+1 dimensions. The dynamics of this model shows that the presence ofinfinitesimal wormholes leads to a decrease in the effective cosmologicalconstant. Similar ideas have been considered in the past by Coleman and othersin the formal setting of 4D Euclidean path integrals. A remarkable property ofthe model is that in the continuum limit we obtain a finite space-time densityof microscopic wormholes without assuming fundamental discreteness. This showsthat one can in principle make sense out of a gravitational path integralincluding a sum over topologies, provided one imposes suitable kinematicalrestrictions on the state-space that preserve large scale causality.Comment: 10 pages, 4 figures. Talk given by S. Zohren at the Albert Einstein  Century International Conference (Paris, July 18-22 2005

Nonperturbative sum over topologies in 2D Lorentzian quantum gravity