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The study of general two dimensional models of gravity allows to tackle basic questions of quantum gravity, bypassing important technical complications which make the treatment in higher dimensions difficult. As the physically important…

High Energy Physics - Theory · Physics 2010-11-19 D. Grumiller , W. Kummer , D. V. Vassilevich

This work investigates the cosmology of a thick brane within the context of $f(\mathbb{Q})$ gravity, an extension of symmetric teleparallelism. Using a five-dimensional Friedmann-Lema\^itre-Robertson-Walker metric, we solve the field…

General Relativity and Quantum Cosmology · Physics 2026-03-05 J. J. Ramos , J. E. G. Silva

We investigate the geodesic structure of realistic static and spherically symmetric spacetimes embedding neutron stars in metric $f(R)$ gravity, focusing on the quadratic Starobinsky model $f(R)=aR^2$ with $a<0$. Neutron-star solutions are…

General Relativity and Quantum Cosmology · Physics 2026-03-10 Néstor Rivero González , Álvaro de la Cruz Dombriz , Gonzalo J. Olmo

Mixed fermion-boson stars are stable, horizonless, everywhere regular solutions of the coupled Einstein-(complex, massive) Klein-Gordon-Euler system. While isolated neutron stars and boson stars are uniquely determined by their central…

General Relativity and Quantum Cosmology · Physics 2022-03-14 Fabrizio Di Giovanni , Nicolas Sanchis-Gual , Pablo Cerdá-Durán , José Antonio Font

In the present paper we investigate non-perturbatively and self-consistently the structure of neutron stars in $R$-squared gravity by simultaneously solving the interior and exterior problem. The mass-radius relations are obtained for…

General Relativity and Quantum Cosmology · Physics 2015-06-18 Stoytcho S. Yazadjiev , Daniela D. Doneva , Kostas D. Kokkotas , Kalin V. Staykov

We investigate the properties of interacting Q-balls and boson stars that sit on top of each other in great detail. The model that describes these solutions is essentially a (gravitating) two-scalar field model where both scalar fields are…

General Relativity and Quantum Cosmology · Physics 2009-09-25 Yves Brihaye , Thierry Caebergs , Betti Hartmann , Momchil Minkov

Theoretical models of self-interacting dark matter offer a promising solution to several unresolved issues within the collisionless cold dark matter framework. For asymmetric dark matter, these self-interactions may encourage gravitational…

General Relativity and Quantum Cosmology · Physics 2025-01-31 Mariachiara Celato , Christian J. Krüger , Kostas D. Kokkotas

We construct a model for dilatonic brane worlds with constant curvature on the brane, i.e. a non-zero four-dimensional cosmological constant, given in function of the dilaton coupling and the cosmological constant of the bulk. We compare…

High Energy Physics - Theory · Physics 2010-04-06 Natxo Alonso-Alberca , Bert Janssen , Pedro J. Silva

Under the influence of gravity, light scalar fields can form bound compact objects called boson stars. We use the technique of matching asymptotic expansions to obtain the profile for boson stars where the constituent particles have…

High Energy Physics - Phenomenology · Physics 2018-06-19 Felix Kling , Arvind Rajaraman

The quantum cosmology of two-dimensional dilaton-gravity models is investigated. A class of models is mapped onto the constrained oscillator-ghost-oscillator model. A number of exact and approximate solutions to the corresponding…

General Relativity and Quantum Cosmology · Physics 2008-11-26 James E. Lidsey

This paper discusses the interior distribution of several anisotropic star models coupled with an electromagnetic field in the context of $f(\mathcal{R},\mathcal{T},\mathcal{Q})$ gravity, where…

General Relativity and Quantum Cosmology · Physics 2023-09-15 M. Sharif , Tayyab Naseer

Non-rotating neutron stars are generally treated in theoretical studies as perfect spheres. Such a treatment, however, may not be correct if strong magnetic fields are present (such as for magnetars) and/or the pressure of the matter in the…

Solar and Stellar Astrophysics · Physics 2015-04-14 O. Zubairi , W. Spinella , A. Romero , R. Mellinger , F. Weber , M. Orsaria , G. Contrera

Quark star models with realistic equation of state in nonperturbative $f(R)$ gravity are considered. The mass-radius relation for $f(R)=R+\alpha R^2$ model is obtained. Considering scalar curvature $R$ as an independent function, one can…

General Relativity and Quantum Cosmology · Physics 2015-06-23 A. V. Astashenok , S. Capozziello , S. D. Odintsov

This work provides the first comparison of the symmetron and dilaton fields in white dwarfs. We show how these screening mechanisms behave inside {such stars} and their impact on stellar properties. Employing a custom-developed shooting…

General Relativity and Quantum Cosmology · Physics 2025-05-15 Joan Bachs-Esteban , Ilídio Lopes , Javier Rubio

We study Rotating Boson Star initial data for Numerical Relativity as previously considered by Yoshida and Eriguchi, Lai (arXiv:gr-qc/0410040v2), and Grandclement, Som\'e and Gourgoulhon (arXiv:1405.4837v3). We use a 3 + 1 decomposition as…

General Relativity and Quantum Cosmology · Physics 2021-08-11 Santiago Ontanon , Miguel Alcubierre

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

The aim of this paper is to study the stability of soliton-like static solutions via non-linear simulations in the context of a special class of massive tensor-multi-scalar-theories of gravity whose target space metric admits Killing…

General Relativity and Quantum Cosmology · Physics 2021-09-22 Riccardo Falcone , Daniela D. Doneva , Kostas D. Kokkotas , Stoytcho S. Yazadjiev

We propose that stable boson stars generically fall within an infinite-parameter family of solutions that oscillate on any number of non-commensurate frequencies. We numerically construct two-frequency solutions and explore their parameter…

General Relativity and Quantum Cosmology · Physics 2019-10-02 Matthew Choptuik , Ramon Masachs , Benson Way

Quantum theory of dilaton gravity coupled to a nonlinear sigma model with a maximally symmetric target space is studied in $2+\epsilon$ dimensions. The ultraviolet stable fixed point for the curvature of the nonlinear sigma model demands a…

High Energy Physics - Theory · Physics 2015-06-26 S. Kojima , N. Sakai , Y. Tanii

The main objective of this article is to study the viable compact stellar structures in non-Riemannian geometry, i.e., $f(\mathbb{Q},T)$ theory, where $\mathbb{Q}$ defines the non-metricity and $T$ represents trace of the stress-energy…

General Relativity and Quantum Cosmology · Physics 2024-04-02 M. Zeeshan Gul , M. Sharif , Adeeba Arooj