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We show that the phenomenon of spontaneous scalarization predicted in neutron stars within the framework of scalar-tensor tensor theories of gravity, also takes place in boson stars without including a self-interaction term for the boson…

General Relativity and Quantum Cosmology · Physics 2012-07-30 Miguel Alcubierre , Juan C. Degollado , Dario Nunez , Milton Ruiz , Marcelo Salgado

Proto-neutron stars are born when a highly evolved and massive star collapses under gravity. In this paper, we investigate the spontaneous scalarization in proto-neutron stars. Based on the scalar tensor theory of gravity as well as the…

High Energy Astrophysical Phenomena · Physics 2025-10-08 Fahimeh Rahimi , Zeinab Rezaei

We consider the effect of scalarization on static and slowly rotating neutron stars for a wide variety of realistic equations of state, including pure nuclear matter, nuclear matter with hyperons, hybrid nuclear and quark matter, and pure…

General Relativity and Quantum Cosmology · Physics 2017-09-28 Zahra Altaha Motahar , Jose Luis Blázquez-Salcedo , Burkhard Kleihaus , Jutta Kunz

Cartan $F(R)$ gravity introduces the equivalent scalar-tensor theory by extending the gravity sector. From the solution of the modified Cartan equation leads to the interaction with the scalar field and the fermion. We derived the effective…

General Relativity and Quantum Cosmology · Physics 2025-03-12 Hiroki Sakamoto , Masahiko Taniguchi

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 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 how light scalar fields can change the stellar landscape by triggering a new phase of nuclear matter. Scalars coupled to nucleons can develop a non-trivial expectation value at finite baryon density. This sourcing of a scalar…

High Energy Physics - Phenomenology · Physics 2023-07-28 Reuven Balkin , Javi Serra , Konstantin Springmann , Stefan Stelzl , Andreas Weiler

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

We carry out numerical-relativity simulations of coalescing binary neutron stars in a scalar-tensor theory that admits spontaneous scalarization. We model neutron stars with realistic equations of state. We choose the free parameters of the…

General Relativity and Quantum Cosmology · Physics 2015-06-17 Masaru Shibata , Keisuke Taniguchi , Hirotada Okawa , Alessandra Buonanno

In certain classes of the scalar-Gauss-Bonnet theory strong spacetime curvature in the vicinity of neutron stars and black holes can spontaneously trigger scalarization in the compact object if the coupling strength of the scalar field to…

General Relativity and Quantum Cosmology · Physics 2023-02-24 Hao-Jui Kuan , Alan Tsz-Lok Lam , Daniela D. Doneva , Stoytcho S. Yazadjiev , Masaru Shibata , Kenta Kiuchi

We study the structure of neutron stars in scalar-tensor theories for the nonminimal coupling of the form $(1+\kappa \xi \phi^{2})\cal R$. We solve the hydrostatic equilibrium equations for two different types of scalar field potentials and…

General Relativity and Quantum Cosmology · Physics 2019-04-02 A. Savaş Arapoğlu , K. Yavuz Ekşi , A. Emrah Yükselci

We compute families of spherically symmetric neutron-star models in two-derivative scalar-tensor theories of gravity with a massive scalar field. The numerical approach we present allows us to compute the resulting spacetimes out to…

General Relativity and Quantum Cosmology · Physics 2021-05-21 Roxana Rosca-Mead , Christopher J. Moore , Ulrich Sperhake , Michalis Agathos , Davide Gerosa

The masses and radii of neutron stars are discussed in general relativity and scalar-tensor theory of gravity and the differences are compared with the current uncertainties stemming from the nuclear equation of state in the relativistic…

General Relativity and Quantum Cosmology · Physics 2019-07-16 F. J. Fattoyev

We present the first numerical models of differentially rotating stars in alternative theories of gravity. We chose a particular class of scalar-tensor theories of gravity that is indistinguishable from GR in the weak field regime but can…

General Relativity and Quantum Cosmology · Physics 2018-12-05 Daniela D. Doneva , Stoytcho S. Yazadjiev , Nikolaos Stergioulas , Kostas D. Kokkotas

Spontaneous scalarization of neutron stars has been extensively studied in the Damour and Esposito-Far\`ese model, in which a scalar field couples to the Ricci scalar or, equivalently, to the trace of the energy-momentum tensor. However,…

General Relativity and Quantum Cosmology · Physics 2024-11-13 Giulia Ventagli , Georgios Antoniou , Antoine Lehébel , Thomas P. Sotiriou

We investigate neutron stars in scalar-tensor theories. We examine their secular stability against spherically symmetric perturbations by use of a turning point method. For some choices of the coupling function contained in the theories,…

General Relativity and Quantum Cosmology · Physics 2009-10-31 Tomohiro Harada

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

Scalarization is a mechanism that endows strongly self-gravitating bodies, such as neutron stars and black holes, with a scalar-field configuration. It resembles a phase transition in that the scalar configuration appears only when a…

General Relativity and Quantum Cosmology · Physics 2024-09-11 Daniela D. Doneva , Fethi M. Ramazanoğlu , Hector O. Silva , Thomas P. Sotiriou , Stoytcho S. Yazadjiev

We study slowly-rotating neutron stars in ghost-free massive bigravity. This theory modifies General Relativity by introducing a second, auxiliary but dynamical tensor field that couples to matter through the physical metric tensor through…

General Relativity and Quantum Cosmology · Physics 2018-02-14 Andrew Sullivan , Nicolas Yunes

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