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We study neutron star configurations in a teleparallel gravity model featuring a scalar field coupled to both matter and torsion. In the Einstein frame, the theory includes a derivative coupling between the scalar field and the torsion…

General Relativity and Quantum Cosmology · Physics 2026-03-25 Youcef Kehal , Khireddine Nouicer

In certain classes of the scalar-Gauss-Bonnet theory strong spacetime curvature in the vicinity of neutron stars and black holes can spontaneously trigger scalarization in the compact object if the coupling strength of the scalar field to…

General Relativity and Quantum Cosmology · Physics 2023-02-24 Hao-Jui Kuan , Alan Tsz-Lok Lam , Daniela D. Doneva , Stoytcho S. Yazadjiev , Masaru Shibata , Kenta Kiuchi

We are investigating universal relations between different normalisations of the moment of inertia and the compactness of neutron stars in slow rotation approximation. We study the relations in particular class of massive scalar-sensor…

General Relativity and Quantum Cosmology · Physics 2019-03-27 Dimitar Popchev , Kalin V. Staykov , Daniela D. Doneva , Stoytcho S. Yazadjiev

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

Hybrid neutron stars, the compact objects consisting hadronic matter and strange quark matter, can be considered as the probes for the scalar tensor gravity. In this work, we explore the scalarization of hybrid neutron stars in the scalar…

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

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

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

We carry out numerical-relativity simulations of coalescing binary neutron stars in a scalar-tensor theory that admits spontaneous scalarization. We model neutron stars with realistic equations of state. We choose the free parameters of the…

General Relativity and Quantum Cosmology · Physics 2015-06-17 Masaru Shibata , Keisuke Taniguchi , Hirotada Okawa , Alessandra Buonanno

There has been a recent revival in understanding the spontaneous scalarization phenomenon in scalar-tensor gravity as a phase transition. Using the tools of the Landau theory, we now know that first-order transitions where scalarization…

General Relativity and Quantum Cosmology · Physics 2026-04-24 Kalin V. Staykov , Fethi M. Ramazanoğlu , Daniela D. Doneva , Stoytcho S. Yazadjiev

Scalar-tensor theories of gravity are extensions of General Relativity (GR) including an extra, nonminimally coupled scalar degree of freedom. A wide class of these theories, albeit indistinguishable from GR in the weak field regime,…

General Relativity and Quantum Cosmology · Physics 2016-06-23 Raissa F. P. Mendes , Néstor Ortiz

We investigate the internal structure and the mass-radius relation of neutron stars in a recently proposed scalar-tensor theory dubbed asymmetron in which a massive scalar field undergoes spontaneous scalarization inside neutron stars. We…

General Relativity and Quantum Cosmology · Physics 2017-11-08 Soichiro Morisaki , Teruaki Suyama

Compact stars in scalar-tensor (ST) gravity have been extensively investigated, but relatively few studies have focused on highly relativistic neutron stars (NSs) with an extremely dense core region where the trace of the energy-momentum…

General Relativity and Quantum Cosmology · Physics 2025-11-14 Peixiang Ji , Lijing Shao

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

We compute the axial quasi-normal modes of static neutron stars in scalar tensor theory. In particular, we employ various realistic equations of state including nuclear, hyperonic and hybrid matter. We investigate the fundamental curvature…

General Relativity and Quantum Cosmology · Physics 2018-08-29 Zahra Altaha Motahar , Jose Luis Blázquez-Salcedo , Burkhard Kleihaus , Jutta Kunz

In the scalar-tensor theories with a massive scalar field the coupling constants, and the coupling functions in general, which are observationally allowed, can differ significantly from those in the massless case. This fact naturally…

General Relativity and Quantum Cosmology · Physics 2016-04-27 Stoytcho S. Yazadjiev , Daniela D. Doneva , Dimitar Popchev

Spontaneous scalarization of neutron stars has been extensively studied in the Damour and Esposito-Far\`ese model, in which a scalar field couples to the Ricci scalar or, equivalently, to the trace of the energy-momentum tensor. However,…

General Relativity and Quantum Cosmology · Physics 2024-11-13 Giulia Ventagli , Georgios Antoniou , Antoine Lehébel , Thomas P. Sotiriou

Motivated by constant-G theory, we introduce a one-parameter family of scalar-tensor theories as an extension of constant-G theory in which the conformal symmetry is a cosmological attractor. Since the model has the coupling function of…

General Relativity and Quantum Cosmology · Physics 2022-01-21 Takeshi Chiba

We calculate moment of inertia of neutron star with different exotic constituents such as hyperons and (anti)kaon condensates and study its variation with mass and spin frequency. The sets of equation of state, generated within the…

High Energy Astrophysical Phenomena · Physics 2017-06-14 S. S. Lenka , P. Char , S. Banik

The merger remnant of a binary neutron star coalescence is initially strongly differentially rotating. Some properties of these remnants can be accurately modeled through building equilibrium neutron star models. In the present paper, we…

General Relativity and Quantum Cosmology · Physics 2023-08-02 Kalin V. Staykov , Daniela D. Doneva , Lavinia Heisenberg , Nikolaos Stergioulas , Stoytcho S. Yazadjiev

Scalar-tensor theories of gravity are natural phenomenological alternatives to General Relativity, where the gravitational interaction is mediated by a scalar degree of freedom, besides the usual tensor gravitons. In regions of the…

General Relativity and Quantum Cosmology · Physics 2013-04-29 Enrico Barausse , Carlos Palenzuela , Marcelo Ponce , Luis Lehner
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