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Title: The role of vector fields in modified gravity scenarios

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
Resource Relation:
Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2013; Journal Issue: 11; Other Information: Country of input: International Atomic Energy Agency (IAEA)
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