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Soft Gamma-Ray Repeaters and Anomalous X-Ray Pulsars are extreme manifestations of the most magnetized neutron stars: magnetars. The phenomenology of their emission and spectral properties strongly support the idea that the magnetospheres…

High Energy Astrophysical Phenomena · Physics 2015-06-23 A. G. Pili , N. Bucciantini , L. Del Zanna

We construct general relativistic models of stationary, strongly magnetized neutron stars. The magnetic field configuration, obtained by solving the relativistic Grad-Shafranov equation, is a generalization of the twisted torus model…

Solar and Stellar Astrophysics · Physics 2015-05-18 R. Ciolfi , V. Ferrari , L. Gualtieri

The densities in the cores of the neutron stars (NSs) can reach several times that of the nuclear saturation density. The exact nature of matter at these densities is still virtually unknown. We consider a number of proposed,…

High Energy Astrophysical Phenomena · Physics 2024-02-16 Zenia Zuraiq , Banibrata Mukhopadhyay , Fridolin Weber

Now the hypothesis of existence of scalar fields of a various nature and energy density in the modern Universe is intensively explored. It can explain a nature of the dark (non- baryon) matter in the Universe and an existence of positive…

High Energy Physics - Phenomenology · Physics 2007-05-23 V. Folomeev , V. Gurovich , R. Usupov

Compact relativistic stars allow us to study the nature of matter under extreme conditions, probing regions of parameter space that are otherwise inaccessible. Nuclear theory in this regime is not well constrained: one key issue is whether…

Astrophysics · Physics 2008-11-26 Anna L. Watts , Sanjay Reddy

$f(R)$ theories of gravity are one of the most popular alternative explanations for dark energy and therefore studying the possible astrophysical implications of these theories is an important task. In the present paper we make a…

General Relativity and Quantum Cosmology · Physics 2015-06-23 Stoytcho S. Yazadjiev , Daniela D. Doneva , Kostas D. Kokkotas

Scalar-tensor theories of gravity are known to allow significant deviations from general relativity through various astrophysical phenomena. In this paper, we formulate a scalar-connection gravity by setting up scalars and connection…

General Relativity and Quantum Cosmology · Physics 2021-01-21 Hemza Azri , Salah Nasri

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

A thorough understanding of properties of neutron stars requires both a reliable knowledge of the equation of state (EOS) of super-dense nuclear matter and the strong-field gravity theories simultaneously. To provide information that may…

Nuclear Theory · Physics 2016-04-21 Xiao-Tao He , F. J. Fattoyev , Bao-An Li , W. G. Newton

Results from helically symmetric scalar field models and first results from a convergent helically symmetric binary neutron star code are reported here; these are models stationary in the rotating frame of a source with constant angular…

General Relativity and Quantum Cosmology · Physics 2009-11-11 Shin'ichirou Yoshida , Benjamin C. Bromley , Jocelyn S. Read , Koji Uryu , John L. Friedman

We present a framework for nonlinearly coupled scalar-tensor theory of gravity to address both inflation and core-collapse supernova problems. The unified approach is based on a novel dynamical trapping and relaxation of scalar gravity in…

General Relativity and Quantum Cosmology · Physics 2013-09-16 C. H. -T. Wang , A. O. Hodson , A. St J. Murphy , T. B. Davies , J. T. Mendonca , R. Bingham

We discuss neutron stars with strong magnetic mean fields in the framework of Extended Theories of Gravity. In particular, we take into account models derived from $f(R)$ and $f(\cal G)$ extensions of General Relativity where functions of…

General Relativity and Quantum Cosmology · Physics 2015-06-22 Artyom V. Astashenok , Salvatore Capozziello , Sergei D. Odintsov

The observation of the x-ray pulse profile emitted by hotspots on the surface of neutron stars offers a unique tool to measure the bulk properties of these objects, including their masses and radii. The x-ray emission takes place at the…

General Relativity and Quantum Cosmology · Physics 2019-03-06 Hector O. Silva , Nicolás Yunes

We point out that a spontaneous scalarized inspiring double neutron star (DNS) system can provide us a natural laboratory to investigate the generation mechanism of masses for gravitons. Because of the appearance of a gravitational scalar…

High Energy Astrophysical Phenomena · Physics 2019-11-12 Jing Wang

We study a scalar field in the background of a holographic neutron star at finite temperature and analyze its asymptotic behavior to compute the two-point correlator at the boundary. From the normal modes of the field we determine the…

High Energy Physics - Theory · Physics 2023-02-24 Tobías Canavesi , Octavio Fierro , Nicolás Grandi , Pablo Pisani

In nonminimally coupled theories where a scalar field is coupled to the Ricci scalar, neutron stars (NSs) can have scalar charges through an interaction with matter mediated by gravity. On the other hand, the same theories do not give rise…

General Relativity and Quantum Cosmology · Physics 2025-03-03 Hiroki Takeda , Shinji Tsujikawa , Atsushi Nishizawa

The quasiperiodic oscillations found in the three giant flares of soft gamma-ray repeaters observed to date have been interpreted as crustal oscillations caused by a starquake following a dramatic rearrangement of the stellar magnetic…

High Energy Astrophysical Phenomena · Physics 2019-09-13 Gibran H. de Souza , Cecilia Chirenti

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

Nuclear matter and neutron stars are studied in the framework of an extended relativistic mean-field (RMF) model with higher-order derivative and density dependent couplings of nucleons to the meson fields. The derivative couplings lead to…

Nuclear Theory · Physics 2015-05-20 Sofija Antić , Stefan Typel

Within scalar-tensor (ST) theories, neutron stars in binary systems experience tidal deformations caused by both their companion and the scalar field. These deformations are strongly correlated to the star's internal structure and…

General Relativity and Quantum Cosmology · Physics 2026-04-20 Eve Dones , Laura Bernard