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We make use of isospin constraints to study the parametric coupling model and the properties of asymmetric nuclear matter. Besides the usual constraints for nuclear matter - effective nucleon mass and the incompressibility at saturation…

We present the field equations governing the equilibrium of rapidly rotating neutron stars in scalar-tensor theories of gravity, as well as representative numerical solutions. The conditions for the presence of a nontrivial scalar field and…

General Relativity and Quantum Cosmology · Physics 2014-02-25 Daniela D. Doneva , Stoytcho S. Yazadjiev , Nikolaos Stergioulas , Kostas D. Kokkotas

The spectrum of oscillating compact objects can be considerably altered in alternative theories of gravity. In particular, it may be enriched by modes with no counterpart in general relativity, tied to the dynamics of additional degrees of…

General Relativity and Quantum Cosmology · Physics 2022-01-21 Raissa F. P. Mendes , Néstor Ortiz , Nikolaos Stergioulas

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 show that, as a result of non-linear self-interactions, it is feasible, at least in light of the bounds coming from terrestrial tests of gravity, measurements of the Casimir force and those constraints imposed by the physics of compact…

High Energy Physics - Phenomenology · Physics 2008-11-26 David F. Mota , Douglas J. Shaw

We study the cosmology of multi-field Dark Energy, using a well-motivated axio-dilaton model that contains the minimal number of fields to have the 2-derivative sigma-model interactions that power-counting arguments show naturally compete…

High Energy Physics - Theory · Physics 2025-05-09 Adam Smith , Philippe Brax , Carsten van de Bruck , C. P. Burgess , Anne-Christine Davis

We argue that the acoustic damping of the matter power spectrum is not a generic feature of the kinetic decoupling of dark matter, but even the enhancement can be realized depending on the nature of the kinetic decoupling when compared to…

Cosmology and Nongalactic Astrophysics · Physics 2018-02-14 Ayuki Kamada , Tomo Takahashi

Dark matter can capture in neutron stars from scattering off ultra-relativistic electrons. We present a method to calculate the capture rate on degenerate targets with ultra-relativistic momenta in a compact astronomical object. Our…

High Energy Physics - Phenomenology · Physics 2020-12-09 Aniket Joglekar , Nirmal Raj , Philip Tanedo , Hai-Bo Yu

A new class of relativistic stellar structure equations which include the effects of an energy-dependent Newton coupling is presented. Significant modifications in the mass-radius relation for neutron stars are possible only if the running…

General Relativity and Quantum Cosmology · Physics 2020-01-16 Alfio Bonanno , Roberto Casadio , Alessia Platania

We analyze the coupling between the internal degrees of freedom of neutron stars in a close binary, and the stars' orbital motion. Our analysis is based on the method of matched asymptotic expansions and is valid to all orders in the…

General Relativity and Quantum Cosmology · Physics 2009-10-30 Eanna E. Flanagan

Scalar-tensor theories (STTs) are a widely studied alternative to General Relativity (GR) in which gravity is endowed with an additional scalar degree of freedom. Although severely constrained by solar system and pulsar timing experiments,…

General Relativity and Quantum Cosmology · Physics 2015-03-13 Raissa F. P. Mendes

We investigate the properties of isospin-symmetric nuclear matter and neutron stars in a chiral model approach adopting the SU(2) parity doublet formulation. This ansatz explicitly incorporates chiral symmetry restoration with the limit of…

Nuclear Theory · Physics 2008-11-26 V. Dexheimer , S. Schramm , D. Zschiesche

We study the role of the effective Coulomb interaction strength and length on the dynamics of nucleons in conditions according to those in a neutron star's crust. Calculations were made with a semi-classical molecular dynamics model,…

Nuclear Theory · Physics 2014-05-14 P. N. Alcain , P. A. Giménez Molinelli , J. I. Nichols , C. O. Dorso

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

A role of the scalar-matter direct coupling in the evolution of scalar-tensor gravity was studied. If the coupling functions in the generalized scalar-tensor gravity satisfy a definite equation the scalar-tensor gravity is reduced to…

General Relativity and Quantum Cosmology · Physics 2019-12-25 Kim Jik-su , Kim Chol-jun

We study the effects of dark matter on the structural properties of neutron stars. In particular we investigate how the presence of a dark matter component influences the mass-radius relation, the value of the maximum mass of a neutron star…

High Energy Astrophysical Phenomena · Physics 2025-05-29 Domenico Scordino , Ignazio Bombaci

We study torsional oscillations of neutron stars in the scalar-tensor theory of gravity using the relativistic Cowling approximation. We compute unperturbed neutron star models adopting realistic equations of state for the neutron star's…

General Relativity and Quantum Cosmology · Physics 2014-12-24 Hector O. Silva , Hajime Sotani , Emanuele Berti , Michael Horbatsch

We study the interaction of massless scalar fields with self-gravitating neutron stars by means of fully dynamic numerical simulations of the Einstein-Klein-Gordon perfect fluid system. Our investigation is restricted to spherical symmetry…

General Relativity and Quantum Cosmology · Physics 2009-11-07 Florian Siebel , Jose A. Font , Philippos Papadopoulos

A scalar-tensor theory of gravity is considered wherein the gravitational coupling $G$ and the speed of light $c$ are admitted as space-time functions and combine to form the definition of the scalar field $\phi$. The varying $c$…

General Relativity and Quantum Cosmology · Physics 2023-04-05 Rodrigo R. Cuzinatto , Rajendra P. Gupta , Pedro J. Pompeia

In this lecture, we give a first introduction to neutron stars, based on fundamental physical principles. After outlining their outstanding macroscopic properties, as obtained from observations, we infer the extreme conditions of matter in…

High Energy Astrophysical Phenomena · Physics 2016-09-27 Pierre M. Pizzochero