Structure of Neutron Stars in Massive Scalar-Tensor Gravity
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.
Additional Information
© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). Received: 23 July 2020; Accepted: 14 August 2020; Published: 19 August 2020. We thank Hector Okada da Silva, Fethi Ramazanoğlu, and Christian Ott for discussions. This research was funded by the European Union's H2020 ERC Consolidator Grant "Matter and strong-field gravity: new frontiers in Einstein's theory" Grant No. MaGRaTh–646597 and the STFC Consolidator Grant No. ST/P000673/1, the GWverse COST Action Grant No. CA16104, "Black holes, gravitational waves and fundamental physics". D.G. is supported by Leverhulme Trust Grant No. RPG-2019-350, M.A. is supported by the Kavli Foundation, Computational work was performed on the SDSC Comet and TACC Stampede2 clusters through NSF-XSEDE Grant No. PHY-090003; the Cambridge CSD3 system through STFC capital Grants No. ST/P002307/1 and No. ST/R002452/1, and STFC operations Grant No. ST/R00689X/1; the University of Birmingham BlueBEAR cluster; the Athena cluster at HPC Midlands+ funded by EPSRC Grant No. EP/P020232/1; and the Maryland Advanced Research Computing Center (MARCC). Author Contributions: Conceptualization, R.R.-M., C.J.M., U.S., M.A. and D.G.; methodology, R.R.-M. and U.S.; software, R.R.-M. and U.S.; validation, R.R.-M. and U.S.; formal analysis and investigation, R.R.-M., C.J.M., U.S., M.A. and D.G.; writing–original draft preparation, R.R.-M. and U.S.; writing–review and editing, R.R.-M., C.J.M., U.S., M.A. and D.G.; project administration, C.J.M., U.S. All authors have read and agreed to the published version of the manuscript. The authors declare no conflict of interest.Attached Files
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Additional details
- Eprint ID
- 105140
- Resolver ID
- CaltechAUTHORS:20200828-112547312
- MaGRaTh-646597
- European Research Council (ERC)
- ST/P000673/1
- Science and Technology Facilities Council (STFC)
- CA16104
- European Cooperation in Science and Technology (COST)
- RPG-2019-350
- Leverhulme Trust
- Kavli Foundation
- PHY-090003
- NSF
- ST/P002307/1
- Science and Technology Facilities Council (STFC)
- ST/R002452/1
- Science and Technology Facilities Council (STFC)
- ST/R00689X/1
- Science and Technology Facilities Council (STFC)
- University of Birmingham
- EP/P020232/1
- Engineering and Physical Sciences Research Council (EPSRC)
- Maryland Advanced Research Computing Center
- Created
-
2020-08-28Created from EPrint's datestamp field
- Updated
-
2021-11-16Created from EPrint's last_modified field
- Caltech groups
- TAPIR