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

We present an overview of a recently suggested new model of quantum initialconditions for the Universe in the form of a cosmological density matrix. Thisdensity matrix originally suggested in the Euclidean quantum gravity frameworkturns out to describe the microcanonical ensemble in the Lorentzian quantumgravity of spatially closed cosmological models. This ensemble represents anequipartition in the physical phase space of the theory (sum over everything),but in terms of the observable spacetime geometry it is peaked about a set ofcosmologies limited to a bounded range of the cosmological constant. Thissuggests a mechanism to constrain the landscape of string vacua and a possiblesolution to the dark energy problem in the form of the quasi-equilibrium decayof the microcanonical state of the Universe. The effective Friedmann equationgoverning this decay incorporates the effect of the conformal anomaly ofquantum fields and features a new mechanism for a cosmological accelerationstage -- big boost scenario. We also briefly discuss the relation between ourmodel, the AdS/CFT correspondence and RS and DGP braneworlds.

Density matrix of the Universe reloaded: origin of inflation and cosmological acceleration