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Published October 22, 2015 | Submitted
Journal Article Open

Tensor-multi-scalar theories: relativistic stars and 3 + 1 decomposition

Abstract

Gravitational theories with multiple scalar fields coupled to the metric and each other—a natural extension of the well studied single-scalar-tensor theories—are interesting phenomenological frameworks to describe deviations from general relativity in the strong-field regime. In these theories, the N-tuple of scalar fields takes values in a coordinate patch of an N-dimensional Riemannian target-space manifold whose properties are poorly constrained by weak-field observations. Here we introduce for simplicity a non-trivial model with two scalar fields and a maximally symmetric target-space 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 scalar-matter coupling matrix, and that the properties of strongly scalarized stellar configurations additionally depend on the target-space curvature radius. In preparation for numerical relativity simulations, we also write down the 3 + 1 decomposition of the field equations for generic tensor-multi-scalar theories.

Additional Information

© 2015 IOP Publishing Ltd. Received 8 June 2015, revised 11 August 2015. Accepted for publication 20 August 2015. Published 23 September 2015. M H, H O S and E B were funded by NSF CAREER Grant No. PHY-1055103. M H would like to acknowledge financial support from the European Research Council under the European Unions Seventh Framework Programme (FP7/2007-2013) / ERC grant agreement n. 306425 'Challenging General Relativity'. P P was supported by the European Community through the Intra-European Marie Curie Contract No. AstroGRAphy-2013-623439 and by FCT-Portugal through the project IF/00293/2013. E B was supported by FCT contract IF/00797/2014/CP1214/CT0012 under the IF2014 Programme. D G is supported by the UK STFC and the Isaac Newton Studentship of the University of Cambridge. U S acknowledges support by the FP7-PEOPLE-2011-CIG Grant No. 293412, H2020 ERC Consolidator Grant 1224 Agreement No. MaGRaTh-646597, SDSC and TACC through XSEDE Grant No. PHY-090003 by the NSF, Finis Terrae through Grant No. ICTS-CESGA-249, STFC Roller Grant No. ST/L000636/1 and DiRACʼs Cosmos Shared Memory system through BIS Grant No. ST/J005673/1 and STFC Grant Nos. ST/H008586/1, ST/K00333X/1. This work was supported by the H2020-MSCA-RISE-2015 Grant No. StronGrHEP-690904. We thank the support teams of Cambridgeʼs Cosmos system, SDSCʼs Trestles, TACCʼs Stampede and CESGAʼs Finis Terrae clusters where computations have been performed. This work was partially supported by NewCompStar (COST Action MP1304) and by the FP7-PEOPLE 2011-IRSES Grant No. 295189 NRHEP.

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August 20, 2023
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October 25, 2023