Tensormultiscalar theories: relativistic stars and 3 + 1 decomposition
Abstract
Gravitational theories with multiple scalar fields coupled to the metric and each othera natural extension of the well studied singlescalartensor theoriesare interesting phenomenological frameworks to describe deviations from general relativity in the strongfield regime. In these theories, the Ntuple of scalar fields takes values in a coordinate patch of an Ndimensional Riemannian targetspace manifold whose properties are poorly constrained by weakfield observations. Here we introduce for simplicity a nontrivial model with two scalar fields and a maximally symmetric targetspace manifold. Within this model we present a preliminary investigation of spontaneous scalarization for relativistic, perfect fluid stellar models in spherical symmetry. We find that the scalarization threshold is determined by the eigenvalues of a symmetric scalarmatter coupling matrix, and that the properties of strongly scalarized stellar configurations additionally depend on the targetspace curvature radius. In preparation for numerical relativity simulations, we also write down the 3 + 1 decomposition of the field equations for generic tensormultiscalar theories.
 Publication:

Classical and Quantum Gravity
 Pub Date:
 October 2015
 DOI:
 10.1088/02649381/32/20/204001
 arXiv:
 arXiv:1505.07462
 Bibcode:
 2015CQGra..32t4001H
 Keywords:

 gravity;
 modified theories;
 neutron stars;
 black holes;
 04.20.q;
 04.40.Dg;
 04.50.Kd;
 04.80.Cc;
 General Relativity and Quantum Cosmology;
 Astrophysics  High Energy Astrophysical Phenomena;
 High Energy Physics  Phenomenology;
 High Energy Physics  Theory
 EPrint:
 32 pages, 8 figures, 1 table, invited contribution to the Classical and Quantum Gravity Focus Issue "Black holes and fundamental fields". v3: version in press in CQG, with various improvements in response to the referees' comments. In particular, the 3+1 decomposition now allows for matter