Perfect fluid Lagrangian and its cosmological implications in theories of gravity with nonminimally coupled matter fields

• Type: Article in International Scientific Journal
• Date: 2018

Authors

Avelino, PP (Author) FCUP; Azevedo, RPL (Author) Other

Journal

Title: Physical Review D

Vol. 97

ISSN: 2470-0010

Publisher: American Physical Society

Indexing

ISI Web of Knowledge - 30 Citations

Scopus - 33 Citations

Other information

Authenticus ID: P-00N-TDV

DOI: 10.1103/physrevd.97.064018

Abstract (EN): In this paper we show that the on-shell Lagrangian of a perfect fluid depends on microscopic properties of the fluid, giving specific examples of perfect fluids with different on-shell Lagrangians but with the same energy-momentum tensor. We demonstrate that if the fluid is constituted by localized concentrations of energy with fixed rest mass and structure (solitons) then the average on-shell Lagrangian of a perfect fluid is given by L-m = T, where T is the trace of the energy-momentum tensor. We show that our results have profound implications for theories of gravity where the matter Lagrangian appears explicitly in the equations of motion of the gravitational and matter fields, potentially leading to observable deviations from a nearly perfect cosmic microwave background black body spectrum: n-type spectral distortions, affecting the normalization of the spectral energy density. Finally, we put stringent constraints on f(R, L-m) theories of gravity using the COBE-FIRAS measurement of the spectral radiance of the cosmic microwave background.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 6