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Structure of Neutron Stars in Massive Scalar-Tensor Gravity

Rosca-Mead, Roxana and Moore, Christopher J. and Sperhake, Ulrich and Agathos, Michalis and Gerosa, Davide (2020) Structure of Neutron Stars in Massive Scalar-Tensor Gravity. Symmetry, 12 (9). Art. No. 1384. ISSN 2073-8994.

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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.

Item Type:Article
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URLURL TypeDescription
Rosca-Mead, Roxana0000-0001-5666-1033
Moore, Christopher J.0000-0002-2527-0213
Sperhake, Ulrich0000-0002-3134-7088
Agathos, Michalis0000-0002-9072-1121
Gerosa, Davide0000-0002-0933-3579
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 ( 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.
Funding AgencyGrant Number
European Research Council (ERC)MaGRaTh-646597
Science and Technology Facilities Council (STFC)ST/P000673/1
European Cooperation in Science and Technology (COST)CA16104
Leverhulme TrustRPG-2019-350
Kavli FoundationUNSPECIFIED
Science and Technology Facilities Council (STFC)ST/P002307/1
Science and Technology Facilities Council (STFC)ST/R002452/1
Science and Technology Facilities Council (STFC)ST/R00689X/1
University of BirminghamUNSPECIFIED
Engineering and Physical Sciences Research Council (EPSRC)EP/P020232/1
Maryland Advanced Research Computing CenterUNSPECIFIED
Subject Keywords:modified gravity; scalar-tensor theory; compact objects; relativistic astrophysics
Issue or Number:9
Record Number:CaltechAUTHORS:20200828-112547312
Persistent URL:
Official Citation:Structure of Neutron Stars in Massive Scalar-Tensor Gravity. Symmetry 2020, 12, 1384; doi: 10.3390/sym12091384
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105140
Deposited By: Tony Diaz
Deposited On:28 Aug 2020 21:23
Last Modified:28 Aug 2020 21:23

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