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Spherical neutron star models are studied within tensor-scalar theories of gravity. Particularly, it is shown that, under some conditions on the second derivative of the coupling function and on star's mass, for a given star there exist two…

General Relativity and Quantum Cosmology · Physics 2009-10-31 J. Novak

In this work, we derive novel constraints on scalar-tensor theories from neutrino physics. Spatial variations of the background scalar field effectively generate density and position-dependent Standard Model masses, including neutrinos.…

High Energy Physics - Phenomenology · Physics 2025-12-17 Arturo de Giorgi , Ivan Martinez Soler , Sergio Sevillano Muñoz

We study the existence and structure of static and slowly rotating neutron stars (NSs) in a particular truncation of scalar torsion theory with a scalar field $ \phi $ non-minimally coupled to the torsion scalar, and a potential of the form…

General Relativity and Quantum Cosmology · Physics 2024-12-31 Youcef Kehal , Khireddine Nouicer , Hamza Boumaza

We calculate static and spherically symmetric solutions for the Rastall modification of gravity to describe Neutron Stars (NS). The key feature of the Rastall gravity is the non-conservation of the energy-momentum tensor proportionally to…

General Relativity and Quantum Cosmology · Physics 2016-10-24 A. M. Oliveira , H. E. S. Velten , J. C. Fabris , L. Casarini

Gravitational waves are tiny disturbances in space-time and are a fundamental, although not yet directly confirmed, prediction of General Relativity. Rapidly rotating neutron stars are one of the possible sources of gravitational radiation…

Astrophysics · Physics 2008-12-03 Aaron Worley , Plamen G. Krastev , Bao-An Li

Gravitational theories with multiple scalar fields coupled to the metric and each other --- a natural extension of the well studied single-scalar-tensor theories --- are interesting phenomenological frameworks to describe deviations from…

General Relativity and Quantum Cosmology · Physics 2016-05-02 Michael Horbatsch , Hector O. Silva , Davide Gerosa , Paolo Pani , Emanuele Berti , Leonardo Gualtieri , Ulrich Sperhake

In General Relativity there is a maximum mass allowed for neutron stars that, if exceeded, entails their collapse into a black hole. Its precise value depends on details of the nuclear matter equation of state about which we are much more…

General Relativity and Quantum Cosmology · Physics 2013-05-30 Antonio Dobado , Felipe J. Llanes-Estrada , Jose Antonio Oller

We investigate how current and proposed observations of neutron stars can lead to an understanding of the state of their interiors and the key unknowns: the typical neutron star radius and the neutron star maximum mass. A theoretical…

Astrophysics · Physics 2008-11-26 James M. Lattimer , Maddapa Prakash

Neutron stars harbour extremely powerful magnetic fields, leading to their shape being deformed. Their magnetic deformation depends both on the geometry - and strength - of their internal magnetic field and on their composition, encoded by…

General Relativity and Quantum Cosmology · Physics 2021-10-19 J. Soldateschi , N. Bucciantini , L. Del Zanna

Recently, theoretical studies on the bumblebee gravity model, a nonminimally-coupled vector-tensor theory that violates the Lorentz symmetry, have flourished, with a simultaneous increase in the utilization of observations to impose…

General Relativity and Quantum Cosmology · Physics 2024-11-26 Peixiang Ji , Zhuhai Li , Lirui Yang , Rui Xu , Zexin Hu , Lijing Shao

Binary pulsars are a powerful tool for probing strong gravity that still outperforms direct gravitational wave observations in a number of directions due to the remarkable accuracy of the pulsar timing. They can constrain very precisely the…

General Relativity and Quantum Cosmology · Physics 2024-06-26 Petar Y. Yordanov , Kalin V. Staykov , Stoytcho S. Yazadjiev , Daniela D. Doneva

We consider the scalar-tensor theories of gravity extended by the pseudoscalar couplings to matter and gauge fields and derive constraints on the CP-odd combinations of scalar and pseudoscalar couplings from laboratory spin precession…

High Energy Physics - Phenomenology · Physics 2010-01-15 Victor Flambaum , Simon Lambert , Maxim Pospelov

Thermal evolution of neutron stars is studied in the $f(R)=R+\alpha R^{2}$ theory of gravity. We first describe the equations of stellar structure and evolution for a spherically symmetric spacetime plus a perfect fluid at rest. We then…

General Relativity and Quantum Cosmology · Physics 2023-06-08 Martín Nava-Callejas , Dany Page , Mikhail V. Beznogov

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

General properties of neutron stars are briefly reviewed with an emphasis on the indispensability of general relativity in our understanding of these fascinating objects. In Newtonian gravity the pressure within a star merely plays the role…

High Energy Astrophysical Phenomena · Physics 2017-03-02 K. Yavuz Ekşi

We investigate in this paper the structures of neutron stars under the strong magnetic field in the framework of $f(T)$ gravity where $T$ denotes the scalar torsion. The TOV equations in this theory of gravity have been considered and…

General Physics · Physics 2017-09-28 M. G. Ganiou , C. Aïnamon , M. J. S. Houndjo , J. Tossa

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

Scalar-tensor theories are one of the most natural and well-constrained alternative theories of gravity, while still allowing for significant deviations from general relativity. We present the equations of motion of nonspinning compact…

General Relativity and Quantum Cosmology · Physics 2023-03-02 Laura Bernard

Theories of gravity in the beyond Horndeski class encompass a wide range of scalar-tensor theories that will be tested on cosmological scales over the coming decade. In this work, we investigate the possibility of testing them in the…

General Relativity and Quantum Cosmology · Physics 2017-03-15 Jeremy Sakstein , Eugeny Babichev , Kazuya Koyama , David Langlois , Ryo Saito

We discuss the stability and construct dynamical configurations describing the gravitational collapse of unstable neutron stars with realistic equations of state compatible with the recent LIGO-Virgo constraints. Unlike other works that…

General Relativity and Quantum Cosmology · Physics 2020-06-17 J. M. Z. Pretel , M. F. A. da Silva