Entropy of Null Surfaces and Dynamics of Spacetime
| dc.creator | Padmanabhan, T. | |
| dc.creator | Paranjape, Aseem | |
| dc.date | 2006-12-30 | |
| dc.date | 2007-01-11 | |
| dc.date.accessioned | 2026-07-07T10:37:10Z | |
| dc.date.available | 2026-07-07T10:37:10Z | |
| dc.description | The null surfaces of a spacetime act as one-way membranes and can block information for a corresponding family of observers (time-like curves). Since lack of information can be related to entropy, this suggests the possibility of assigning an entropy to the null surfaces of a spacetime. We motivate and introduce such an entropy functional for any vector field in terms of a fourth-rank divergence free tensor P_{ab}^{cd} with the symmetries of the curvature tensor. Extremising this entropy for all the null surfaces then leads to equations for the background metric of the spacetime. When P_{ab}^{cd} is constructed from the metric alone, these equations are identical to Einstein's equations with an undetermined cosmological constant (which arises as an integration constant). More generally, if P_{ab}^{cd} is allowed to depend on both metric and curvature in a polynomial form, one recovers the Lanczos-Lovelock gravity. In all these cases: (a) We only need to extremise the entropy associated with the null surfaces; the metric is not a dynamical variable in this approach. (b) The extremal value of the entropy agrees with standard results, when evaluated on-shell for a solution admitting a horizon. The role of full quantum theory of gravity will be to provide the specific form of P_{ab}^{cd} which should be used in the entropy functional. With such an interpretation, it seems reasonable to interpret the Lanczos-Lovelock type terms as quantum corrections to classical gravity. | |
| dc.description | revised version with significantly generalised perspective; references added | |
| dc.identifier | https://arxiv.org/abs/gr-qc/0701003 | |
| dc.identifier | http://arxiv.org/abs/gr-qc/0701003 | |
| dc.identifier | Phys.Rev.D75:064004,2007 | |
| dc.identifier | doi:10.1103/PhysRevD.75.064004 | |
| dc.identifier.uri | http://salesiana.dossiersoluciones.com/handle/123456789/180290 | |
| dc.subject | General Relativity and Quantum Cosmology | |
| dc.subject | Astrophysics | |
| dc.subject | High Energy Physics - Theory | |
| dc.title | Entropy of Null Surfaces and Dynamics of Spacetime | |
| dc.type | text |