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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

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

A decade ago, it was shown that a wide class of scalar-tensor theories can pass very restrictive weak field tests of gravity and yet exhibit non-perturbative strong field deviations away from General Relativity. This phenomenon was called…

Astrophysics · Physics 2009-11-10 A. W. Whinnett , Diego F. Torres

Some models (such as the Skyrme model, a low-energy effective field theory for QCD) suggest that the high-density matter prevailing in neutron star interiors may be significantly anisotropic. Anisotropy is known to affect the bulk…

General Relativity and Quantum Cosmology · Physics 2015-06-05 Hector O. Silva , Caio F. B. Macedo , Emanuele Berti , Luís C. B. Crispino

Some recently discovered nonperturbative strong-field effects in tensor-scalar theories of gravitation are interpreted as a scalar analog of ferromagnetism: "spontaneous scalarization". This phenomenon leads to very significant deviations…

General Relativity and Quantum Cosmology · Physics 2016-08-24 Thibault Damour , Gilles Esposito-Farese

We perform the first study of the oscillation frequencies of rapidly rotating neutron stars in alternative theories of gravity, focusing mainly on the fundamental $f$-modes. We concentrated on a particular class of alternative theories -…

General Relativity and Quantum Cosmology · Physics 2017-09-13 Stoytcho S. Yazadjiev , Daniela D. Doneva , Kostas D. Kokkotas

We study the axial quasi-normal modes of neutron stars in scalar-tensor theories with massive scalar field including a self-interacting term in the potential. Various realistic equations of state including nuclear, hyperonic and hybrid…

General Relativity and Quantum Cosmology · Physics 2019-05-08 Zahra Altaha Motahar , Jose Luis Blázquez-Salcedo , Daniela D. Doneva , Jutta Kunz , 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

Scalar fields with inverse power-law effective potentials may provide a negative pressure component to the energy density of the universe today, as required by cosmological observations. In order to be cosmologically relevant today, the…

High Energy Physics - Phenomenology · Physics 2016-09-06 Nicola Bartolo , Massimo Pietroni

Unlike general relativity, the scalar gravitational waves can be excited due to the radial oscillations in scalar-tensor gravity. To examine the scalar gravitational waves in scalar-tensor gravity, we derive the evolution equations of the…

High Energy Astrophysical Phenomena · Physics 2015-06-18 Hajime Sotani

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

Aether Scalar-Tensor theory is a modification of general relativity proposed to explain galactic and cosmological mass discrepancies conventionally attributed to dark matter.~The theory is able to fit the cosmic microwave background and the…

General Relativity and Quantum Cosmology · Physics 2025-02-20 Christopher Reyes , Jeremy Sakstein

We present an alternative way of tracing the existence of a scalar field based on the analysis of the gravitational wave spectrum of a vibrating neutron star. Scalar-tensor theories in strong-field gravity can potentially introduce much…

General Relativity and Quantum Cosmology · Physics 2009-11-10 Hajime Sotani , Kostas D. Kokkotas

We generalize tensor-scalar theories of gravitation by the introduction of an abnormally weighting type of energy. This theory of tensor-scalar anomalous gravity is based on a relaxation of the weak equivalence principle that is now…

Astrophysics · Physics 2009-01-14 J. -M. Alimi , A. Füzfa

We use neutron star mass and radius measurements to constrain the spontaneous scalarization phenomenon in scalar-tensor theories using Bayesian analysis. Neutron star structures in this scenario can be significantly different from the case…

General Relativity and Quantum Cosmology · Physics 2022-07-06 Semih Tuna , Kıvanç İ. Ünlütürk , Fethi M. Ramazanoğlu

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

At the supranuclear densities achieved inside a neutron star, matter may exhibit extreme properties. In particular, it may be the case that a suitable average of the speed of sound squared exceeds the so-called conformal limit, i.e.,…

General Relativity and Quantum Cosmology · Physics 2024-12-02 Raissa F. P. Mendes , Caroline F. Sodré , Felipe T. Falciano

The best motivated alternatives to general relativity are scalar-tensor theories, in which the gravitational interaction is mediated by one or several scalar fields together with the usual graviton. The analysis of their various…

General Relativity and Quantum Cosmology · Physics 2009-11-10 Gilles Esposito-Farese

Neutron stars (NSs) in scalar-tensor theories of gravitation with the phenomenon of spontaneous scalarization can develop significant deviations from general relativity. Cases with a massless scalar were studied widely. Here we compare the…

General Relativity and Quantum Cosmology · Physics 2025-04-01 Zexin Hu , Yong Gao , Rui Xu , Lijing Shao

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