Lagrangian description of perfect fluids and modified gravity with an extra force

2009/12/18 by Valerio Faraoni
Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Solar and Space Plasma Dynamics #astro-ph.GA #gr-qc

paper · pdf · doi:10.1103/physrevd.80.124040

published as Phys.Rev.D80:124040,2009 · 3 pages, LaTex, to appear in Phys. Rev. D. References added

arxiv created 2009/12/18 · openalex publication_date 2009/12/28 · arxiv updated 2010/04/23 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/30

Abstract

We revisit the issue of the correct Lagrangian description of a perfect fluid (L₁=P versus L₂=\ensuremath-\ensuremathρ) in relation with modified gravity theories in which galactic luminous matter couples nonminimally to the Ricci scalar. These Lagrangians are only equivalent when the fluid couples minimally to gravity and not otherwise; in the presence of nonminimal coupling they give rise to two distinct theories with different predictions.

Citations

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• The generalized virial theorem inf(R) gravity
• Is cosmic speed-up due to new gravitational physics?
• Action functionals for relativistic perfect fluids