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 Tools annual

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 Tools monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

The emergent gravity paradigm interprets gravitational field equations asdescribing the thermodynamic limit of the underlying statistical mechanics ofmicroscopic degrees of freedom of the spacetime. The connection is establishedby attributing a heat density Ts to the null surfaces where T is theappropriate Davies-Unruh temperature and s is the entropy density. The fieldequations can be obtained from a thermodynamic variational principle whichextremizes the total heat density of all null surfaces. The explicit form of sdetermines the nature of the theory. We explore the consequences of thisparadigm for an arbitrary null surface and highlight the thermodynamicsignificance of various geometrical quantities. In particular, we show that:(a) A conserved current, associated with the time development vector in anatural fashion, has direct thermodynamic interpretation in allLanczos-Lovelock models of gravity. (b) One can generalize the notion ofgravitational momentum, introduced in arXiv 1506.03814 to all Lanczos-Lovelockmodels of gravity such that the conservation of the total momentum leads to therelevant field equations. (c) The thermodynamic variational principle whichleads to the field equations of gravity can also be expressed in terms of thegravitational momentum in all Lanczos-Lovelock models. (d) Three differentprojections of gravitational momentum related to an arbitrary null surface inthe spacetime lead to three different equations, all of which havethermodynamic interpretation. The first one reduces to a Navier-Stokes equationfor the transverse drift velocity. The second can be written as a thermodynamicidentity TdS = dE + P dV. The third describes the time evolution of the nullsurface in terms of suitably defined surface and bulk degrees of freedom. Theimplications are discussed.

Thermodynamical interpretation of the geometrical variables associated with null surfaces