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Structure of Neutron Stars in Massive Scalar-Tensor Gravity

Published version
Peer-reviewed

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Abstract

We compute families of spherically symmetric neutron-star models in two-derivative scalar-tensor theories of gravity with a massive scalar field. The numerical approach we present allows us to compute the resulting spacetimes out to infinite radius using a relaxation algorithm on a compactified grid. We discuss the structure of the weakly and strongly scalarized branches of neutron-star models thus obtained and their dependence on the linear and quadratic coupling parameters α0, β0 between the scalar and tensor sectors of the theory, as well as the scalar mass μ. For highly negative values of β0, we encounter configurations resembling a “gravitational atom”, consisting of a highly compact baryon star surrounded by a scalar cloud. A stability analysis based on binding-energy calculations suggests that these configurations are unstable and we expect them to migrate to models with radially decreasing baryon density and scalar field strength.

Description

Keywords

modified gravity, scalar-tensor theory, compact objects, relativistic astrophysics

Journal Title

Symmetry

Conference Name

Journal ISSN

2073-8994

Volume Title

12

Publisher

MDPI
Sponsorship
European Research Council (H2020-ERC-2014-CoG MaGRaTh 646597)
Science and Technology Facilities Council (ST/P000673/1, ST/P002307/1, ST/R002452/1, ST/R00689X/1)
European Cooperation in Science and Technology (CA16104)
Leverhulme Trust (RPG-2019-350)
National Science Foundation (PHY-090003)
Engineering and Physical Sciences Research Council (EP/P020232/1)