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Title: The role of vector fields in modified gravity scenarios

Abstract

Gravitational vector degrees of freedom typically arise in many examples of modified gravity models. We start to systematically explore their role in these scenarios, studying the effects of coupling gravitational vector and scalar degrees of freedom. We focus on set-ups that enjoy a Galilean symmetry in the scalar sector and an Abelian gauge symmetry in the vector sector. These symmetries, together with the requirement that the equations of motion contain at most two space-time derivatives, only allow for a small number of operators in the Lagrangian for the gravitational fields. We investigate the role of gravitational vector fields for two broad classes of phenomena that characterize modified gravity scenarios. The first is self-acceleration: we analyze in general terms the behavior of vector fluctuations around self-accelerating solutions, and show that vanishing kinetic terms of vector fluctuations lead to instabilities on cosmological backgrounds. The second phenomenon is the screening of long range fifth forces by means of Vainshtein mechanism. We show that if gravitational vector fields are appropriately coupled to a spherically symmetric source, they can play an important role for defining the features of the background solution and the scale of the Vainshtein radius. Our general results can be applied tomore » any concrete model of modified gravity, whose low-energy vector and scalar degrees of freedom satisfy the symmetry requirements that we impose.« less

Authors:
;  [1];  [2]
  1. Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, PO1 3F (United Kingdom)
  2. Cosmology Group, African Institute for Mathematical Sciences, Muizenberg, 7945 (South Africa)
Publication Date:
OSTI Identifier:
22369918
Resource Type:
Journal Article
Journal Name:
Journal of Cosmology and Astroparticle Physics
Additional Journal Information:
Journal Volume: 2013; Journal Issue: 11; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1475-7516
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; DEGREES OF FREEDOM; EQUATIONS OF MOTION; FLUCTUATIONS; GAUGE INVARIANCE; GRAVITATION; LAGRANGIAN FUNCTION; SCREENING; SPACE-TIME; SYMMETRY; VECTOR FIELDS

Citation Formats

Tasinato, Gianmassimo, Koyama, Kazuya, and Khosravi, Nima. The role of vector fields in modified gravity scenarios. United States: N. p., 2013. Web. doi:10.1088/1475-7516/2013/11/037.
Tasinato, Gianmassimo, Koyama, Kazuya, & Khosravi, Nima. The role of vector fields in modified gravity scenarios. United States. https://doi.org/10.1088/1475-7516/2013/11/037
Tasinato, Gianmassimo, Koyama, Kazuya, and Khosravi, Nima. 2013. "The role of vector fields in modified gravity scenarios". United States. https://doi.org/10.1088/1475-7516/2013/11/037.
@article{osti_22369918,
title = {The role of vector fields in modified gravity scenarios},
author = {Tasinato, Gianmassimo and Koyama, Kazuya and Khosravi, Nima},
abstractNote = {Gravitational vector degrees of freedom typically arise in many examples of modified gravity models. We start to systematically explore their role in these scenarios, studying the effects of coupling gravitational vector and scalar degrees of freedom. We focus on set-ups that enjoy a Galilean symmetry in the scalar sector and an Abelian gauge symmetry in the vector sector. These symmetries, together with the requirement that the equations of motion contain at most two space-time derivatives, only allow for a small number of operators in the Lagrangian for the gravitational fields. We investigate the role of gravitational vector fields for two broad classes of phenomena that characterize modified gravity scenarios. The first is self-acceleration: we analyze in general terms the behavior of vector fluctuations around self-accelerating solutions, and show that vanishing kinetic terms of vector fluctuations lead to instabilities on cosmological backgrounds. The second phenomenon is the screening of long range fifth forces by means of Vainshtein mechanism. We show that if gravitational vector fields are appropriately coupled to a spherically symmetric source, they can play an important role for defining the features of the background solution and the scale of the Vainshtein radius. Our general results can be applied to any concrete model of modified gravity, whose low-energy vector and scalar degrees of freedom satisfy the symmetry requirements that we impose.},
doi = {10.1088/1475-7516/2013/11/037},
url = {https://www.osti.gov/biblio/22369918}, journal = {Journal of Cosmology and Astroparticle Physics},
issn = {1475-7516},
number = 11,
volume = 2013,
place = {United States},
year = {Fri Nov 01 00:00:00 EDT 2013},
month = {Fri Nov 01 00:00:00 EDT 2013}
}