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arXiv · 1505.07462

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

Michael Horbatsch·Hector O. Silva·Davide Gerosa·Paolo Pani·Emanuele Berti·Leonardo Gualtieri·Ulrich Sperhake
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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.

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Michael Horbatsch, Hector O. Silva, Davide Gerosa, Paolo Pani, Emanuele Berti, Leonardo Gualtieri, Ulrich Sperhake. 2015-05-27. Tensor-multi-scalar theories: relativistic stars and 3+1 decomposition. https://doi.org/10.1088/0264-9381%2F32%2F20%2F204001

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