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Dark matter, an important portion of compact objects, can influence different phenomena in neutron stars. The spontaneous scalarization in the scalar-tensor gravity has been proposed for neutron stars. Here, we investigate the spontaneous…

High Energy Astrophysical Phenomena · Physics 2025-10-08 Fahimeh Rahimi , Zeinab Rezaei

The timing of binary pulsars allows us to place some of the tightest constraints on modified theories of gravity. Perhaps some of the most interesting and well-motivated extensions to General Relativity are scalar-tensor theories, in which…

General Relativity and Quantum Cosmology · Physics 2019-09-04 David Anderson , Nicolás Yunes

We study quasi-equilibrium sequences of binary neutron stars in the framework of Damour-Esposito-Farese-type scalar-tensor theory of gravity with a massive scalar field, paying particular attention to the case where neutron stars are…

General Relativity and Quantum Cosmology · Physics 2023-09-06 Hao-Jui Kuan , Karim Van Aelst , Alan Tsz-Lok Lam , Masaru Shibata

Particular couplings between a scalar field and the Gauss-Bonnet invariant lead to spontaneous scalarization of black holes. Here we continue our work on simulating this phenomenon in the context of binary black hole systems. We consider a…

General Relativity and Quantum Cosmology · Physics 2022-08-31 Matthew Elley , Hector O. Silva , Helvi Witek , Nicolás Yunes

We study the nonlinear dynamics of black holes that carry scalar hair and binaries composed of such black holes. The scalar hair is due to a linear or exponential coupling between the scalar and the Gauss--Bonnet invariant. We work…

General Relativity and Quantum Cosmology · Physics 2019-04-03 Helvi Witek , Leonardo Gualtieri , Paolo Pani , Thomas P. Sotiriou

Corrections to general relativity that introduce long-ranged scalar fields which are non-minimally coupled to curvature typically predict that neutron stars possess a non-trivial scalar field profile. An observer far from a star is most…

General Relativity and Quantum Cosmology · Physics 2016-01-18 Kent Yagi , Leo C. Stein , Nicolas Yunes

We investigated scalarization in dark matter stars. In scalar tensor theories, the coupling between matter and a scalar field generates an effective mass, which is known to trigger the growth of the scalar field in stars and black holes…

General Relativity and Quantum Cosmology · Physics 2026-05-26 Junya Tanaka

Spontaneous scalarization is a gravitational phenomenon in which deviations from general relativity arise once a certain threshold in curvature is exceeded, while being entirely absent below that threshold. For black holes, scalarization is…

General Relativity and Quantum Cosmology · Physics 2021-09-08 Georgios Antoniou , Antoine Lehébel , Giulia Ventagli , Thomas P. Sotiriou

In scalar-tensor theories, spontaneous scalarization is a phase transition that can occur in ultra-dense environments such as neutron stars. The scalar field develops a non-trivial configuration once the stars exceeds a compactness…

General Relativity and Quantum Cosmology · Physics 2018-03-21 Nicola Franchini , Andrew Coates , Thomas P. Sotiriou

Scalarization is a mechanism that endows strongly self-gravitating bodies, such as neutron stars and black holes, with a scalar-field configuration. It resembles a phase transition in that the scalar configuration appears only when a…

General Relativity and Quantum Cosmology · Physics 2024-09-11 Daniela D. Doneva , Fethi M. Ramazanoğlu , Hector O. Silva , Thomas P. Sotiriou , Stoytcho S. Yazadjiev

We study the effect of a mass term in the spontaneous scalarization of neutron stars, for a wide range of scalar field parameters and neutron star equations of state. Even though massless scalars have been the focus of interest in…

General Relativity and Quantum Cosmology · Physics 2016-03-09 Fethi M. Ramazanoğlu , Frans Pretorius

We use neutron star mass and radius measurements to constrain the spontaneous scalarization phenomenon in scalar-tensor theories using Bayesian analysis. Neutron star structures in this scenario can be significantly different from the case…

General Relativity and Quantum Cosmology · Physics 2022-07-06 Semih Tuna , Kıvanç İ. Ünlütürk , Fethi M. Ramazanoğlu

Neutron stars are ideal astrophysical sources to probe general relativity due to their large compactnesses and strong gravitational fields. For example, binary pulsar and gravitational wave observations have placed stringent bounds on…

General Relativity and Quantum Cosmology · Physics 2021-08-11 Kent Yagi , Michael Stepniczka

Binary neutron star mergers provide a laboratory for probing fundamental physics through their gravitational-wave emission and electromagnetic counterparts. In particular, they may allow us to explore signatures of physics beyond the…

General Relativity and Quantum Cosmology · Physics 2026-02-17 Rohan Srikanth , Tim Dietrich , Katy Clough

It has recently been shown that nontrivial couplings between a scalar and the Gauss-Bonnet invariant can give rise to black hole spontaneous scalarization. Theories that exhibit this phenomenon are among the leading candidates for testing…

General Relativity and Quantum Cosmology · Physics 2019-05-22 Caio F. B. Macedo , Jeremy Sakstein , Emanuele Berti , Leonardo Gualtieri , Hector O. Silva , Thomas P. Sotiriou

Scalar-tensor gravity models are among the prime candidates to explain cosmic acceleration, and compact stars provide unique laboratories for testing such theories. Predictions of scalar-tensor gravity in compact stars can be examined…

High Energy Astrophysical Phenomena · Physics 2025-10-08 Fahimeh Rahimi , Zeinab Rezaei , Adamu Issifu

It was recently discovered that scalarized neutron stars in scalar-tensor theories can undergo a gravitational phase transition to a non-scalarized (GR) state. Surprisingly, even though the driving mechanism is totally different, the…

General Relativity and Quantum Cosmology · Physics 2023-06-30 Daniela D. Doneva , Christian J. Krüger , Kalin V. Staykov , Petar Y. Yordanov

We study phenomenological features and stability of boson stars in massless and massive scalar-tensor theory of gravity with Damour-Esposito-Farese coupling. This coupling between the tensor and scalar sectors of the theory leads to a…

General Relativity and Quantum Cosmology · Physics 2024-07-29 Tamara Evstafyeva , Roxana Rosca-Mead , Ulrich Sperhake , Bernd Brugmann

Ferromagnetic spin ordering can take place in neutron stars. This phase transition alters the neutron star equation of state. Here, applying the scalar-tensor theories of gravity, we investigate the structure of neutron stars which are in…

High Energy Astrophysical Phenomena · Physics 2019-03-11 Zeinab Rezaei , Habib Yousefi Dezdarani

In the presence of appropriate non-minimal couplings between a scalar field and the curvature squared Gauss-Bonnet (GB) term, compact objects such as neutron stars and black holes (BHs) can spontaneously scalarize, becoming a preferred…

General Relativity and Quantum Cosmology · Physics 2021-04-26 Carlos Herdeiro , Eugen Radu , D. H. Tchrakian