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We present a full 3D numerical evolution code to study neutron stars in massive-scalar-tensor theories. The code is embedded in the Einstein Toolkit framework and its implementation constitutes a modified version of the…

General Relativity and Quantum Cosmology · Physics 2026-05-19 José Carlos Olvera M. , Daniela D. Doneva , Pablo Cerdá-Durán , José A. Font , Stoytcho S. Yazadjiev

We study static, spherically symmetric neutron stars in a class of scalar-tensor theories with non-canonical kinetic terms (K-essence) obeying all causality and hyperbolicity conditions. These models have non-trivial dynamics that lead to a…

General Relativity and Quantum Cosmology · Physics 2025-09-12 Mark P. Hertzberg , Oleksandr S. Stashko

In the present paper we construct novel non-topological, spontaneously scalarized neutron stars in multi-scalar Gauss-Bonnet gravity with maximally symmetric target space, and nontrivial map $\varphi:spacetime \rightarrow target\ space$.…

General Relativity and Quantum Cosmology · Physics 2022-02-23 Kalin V. Staykov , Radostina Z. Zheleva

We present a framework to study generic neutron-star binaries in scalar-tensor theories of gravity. Our formalism achieves this goal by suitably interfacing a post-Newtonian orbital evolution (described by a set of ordinary differential…

General Relativity and Quantum Cosmology · Physics 2014-03-07 Carlos Palenzuela , Enrico Barausse , Marcelo Ponce , Luis Lehner

In the present paper, we numerically construct new non-topological, spontaneously scalarized neutron stars in the tensor-multi-scalar theories of gravity whose target space is a three-dimensional maximally symmetric space, namely either…

General Relativity and Quantum Cosmology · Physics 2020-05-13 Daniela D. Doneva , Stoytcho S. Yazadjiev

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

Differentially rotating scalarized neutron stars, mimickers of binary merger remnants, can possess an enormous angular momentum larger than what could possibly be sustained in a neutron star in general relativity by about one order of…

General Relativity and Quantum Cosmology · Physics 2025-02-07 Alan Tsz-Lok Lam , Kalin V. Staykov , Hao-Jui Kuan , Daniela D. Doneva , Stoytcho S. Yazadjiev

We present a self-consistent, relativistic model of rapidly rotating neutron stars describing their exterior gravitational field. This is achieved by matching the new solution of Einstein's field equations found by Manko et al. (2000) and…

Astrophysics · Physics 2009-11-07 Matthias Stute , Max Camenzind

Scalar-tensor~(ST) theories of gravity are natural phenomenological extensions to general relativity. Although these theories are severely constrained both by solar system experiments and by binary pulsar observations, a large set of ST…

General Relativity and Quantum Cosmology · Physics 2016-02-10 Carlos Palenzuela , Steve Liebling

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

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

Aether Scalar-Tensor theory is a relativistic alternative gravity model that behaves like cold dark matter on cosmological scales while predicting the MOND force-law in astrophysical systems. The theory correctly predicts the cosmic…

General Relativity and Quantum Cosmology · Physics 2025-05-07 Christopher Reyes , Jeremy Sakstein

In this work, we study the influence of $f(R,T)$ gravity on rapidly rotating neutron stars. First we discuss the main aspects of this modified theory of gravity where the gravitational Lagrangian is an arbitrary function of the Ricci scalar…

General Relativity and Quantum Cosmology · Physics 2023-05-03 F. M. da Silva , L. C. N. Santos , C. E. Mota , T. O. F. da Costa , J. C. Fabris

Models of relativistic rotating neutron star composed of hyperon rich matter is constructed in the framework of an effective field theory in the mean-field approach. The gross properties of compact star is calculated at both static and the…

Nuclear Theory · Physics 2009-05-12 B. K. Sharma , T. K. Jha

Modified theories of gravity that offer viable models for dark energy often rely on mechanisms that screen their effects in high density environments. From this perspective, it would appear that, once solar system constraints are satisfied,…

General Relativity and Quantum Cosmology · Physics 2020-07-24 Bernardo F. de Aguiar , Raissa F. P. Mendes

We study the orbital and epicyclic frequencies of particles orbiting around rapidly rotating neutron stars and strange stars in a particular scalar-tensor theory of gravity. We find very large deviations of these frequencies, when compared…

High Energy Astrophysical Phenomena · Physics 2014-08-06 Daniela D. Doneva , Stoytcho S. Yazadjiev , Nikolaos Stergioulas , Kostas D. Kokkotas , Tilemachos M. Athanasiadis

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 study oscillations and instabilities of relativistic stars using perturbation theory in general relativity and take into account the contribution of a dynamic spacetime. We present the oscillation spectrum as well as the critical values…

General Relativity and Quantum Cosmology · Physics 2020-09-16 C. J. Krüger , K. D. Kokkotas

In $f(R)$ gravity and Brans-Dicke theory with scalar potentials, we study the structure of neutron stars on a spherically symmetric and static background for two equations of state: SLy and FPS. In massless BD theory, the presence of a…

General Relativity and Quantum Cosmology · Physics 2019-10-04 Ryotaro Kase , Shinji Tsujikawa

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