Unimodular Einstein--Cartan gravity: Dynamics and conservation laws
| Autor: | Yuri Bonder, Cristóbal Corral |
|---|---|
| Rok vydání: | 2018 |
| Předmět: |
Physics
High Energy Physics - Theory Conservation law Spinor Spacetime 010308 nuclear & particles physics Cartan formalism FOS: Physical sciences Cosmological constant General Relativity and Quantum Cosmology (gr-qc) 01 natural sciences General Relativity and Quantum Cosmology Unimodular matrix Vacuum energy High Energy Physics - Theory (hep-th) 0103 physical sciences 010306 general physics Cosmological constant problem Mathematical physics |
| DOI: | 10.48550/arxiv.1802.04795 |
| Popis: | Unimodular gravity is an interesting approach to address the cosmological constant problem, since the vacuum energy density of quantum fields does not gravitate in this framework, and the cosmological constant appears as an integration constant. These features arise as a consequence of considering a constrained volume element 4-form that breaks the diffeomorphisms invariance down to volume preserving diffeomorphisms. In this work, the first-order formulation of unimodular gravity is presented by considering the spin density of matter fields as a source of spacetime torsion. Even though the most general matter Lagrangian allowed by the symmetries is considered, dynamical restrictions arise on their functional dependence. The field equations are obtained and the conservation laws associated with the symmetries are derived. It is found that, analogous to torsion-free unimodular gravity, the field equation for the vierbein is traceless; nevertheless, torsion is algebraically related to the spin density as in standard Einstein-Cartan theory. The particular example of massless Dirac spinors is studied, and comparisons with standard Einstein-Cartan theory are shown. Comment: 8 pages, 1 Appendix, matches published version |
| Databáze: | OpenAIRE |
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