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We study physical applications of the Bohm metrics, which are infinite sequences of inhomogeneous Einstein metrics on spheres and products of spheres of dimension 5 <= d <= 9. We prove that all the Bohm metrics on S^3 x S^2 and S^3 x S^3…

High Energy Physics - Theory · Physics 2009-10-07 G. W. Gibbons , S. A. Hartnoll , C. N. Pope

We study spherically symmetric solutions to the Einstein-Euler equations which model an idealized relativistic neutron star surrounded by vacuum. These are barotropic fluids with a free boundary, governed by an equation of state which sets…

Analysis of PDEs · Mathematics 2021-08-16 Grigorios Fournodavlos , Volker Schlue

We present our first successful numerical results of 3D general relativistic simulations in which the Einstein equation as well as the hydrodynamic equations are fully solved. This paper is especially devoted to simulations of test problems…

General Relativity and Quantum Cosmology · Physics 2009-10-31 Masaru Shibata

Gravitationally bound structures composed by fermions and scalar particles known as fermion-boson stars are regular and static configurations obtained by solving the coupled Einstein-Klein-Gordon-Euler (EKGE) system. In this work, we…

General Relativity and Quantum Cosmology · Physics 2020-11-04 Fabrizio Di Giovanni , Saeed Fakhry , Nicolas Sanchis-Gual , Juan Carlos Degollado , José A. Font

Excited state soliton stars are studied numerically for the first time. The stability of spherically symmetric S-branch excited state oscillatons under radial perturbations is investigated using a 1D code. We find that these stars are…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Jayashree Balakrishna , Ruxandra Bondarescu , Gregory Daues , Mihai Bondarescu

In general relativity, the Einstein equations provide spherically symmetric static spacetimes with dynamics defined as an evolution along the radial coordinate $r$. The geometrical sector becomes a one-dimensional mechanical system, with…

General Relativity and Quantum Cosmology · Physics 2025-11-03 Etera R. Livine , Yuki Yokokura

We report on general relativistic calculations of quasiequilibrium configurations of binary neutron stars in circular orbits with zero vorticity. These configurations are expected to represent realistic situations as opposed to corotating…

General Relativity and Quantum Cosmology · Physics 2009-10-31 S. Bonazzola , E. Gourgoulhon , J. -A. Marck

In this work, we study the existence of strange star in the background of $f(\mathbb{T},\mathcal{T})$ gravity in the Einstein spacetime geometry, where $\mathbb{T}$ is the torsion tensor and $\mathcal{T}$ is the trace of the energy-momentum…

General Relativity and Quantum Cosmology · Physics 2021-10-13 I. G. Salako , M. Khlopov , Saibal Ray , M. Z. Arouko , Pameli Saha , Ujjal Debnath

We investigate a Bardeen model coupling Einstein gravity with nonlinear electromagnetic fields and non-topological soliton complex scalar fields, governed by the magnetic charge $\tilde{q}$, the complex scalar field frequency…

General Relativity and Quantum Cosmology · Physics 2025-05-14 Zhen-Hua Zhao , Yi-Ning Gu , Shu-Cong Liu , Long-Xing Huang , Yong-Qiang Wang

We study a specific model of anisotropic strange stars in the modified $f\left(R,\mathcal{T}\right)$-type gravity by deriving solutions to the modified Einstein field equations representing a spherically symmetric anisotropic stellar…

General Relativity and Quantum Cosmology · Physics 2019-05-01 Debabrata Deb , Sergei V. Ketov , S. K. Maurya , Maxim Khlopov , P. H. R. S. Moraes , Saibal Ray

After giving an overview of the history and idea of neutron stars, I shall introduce, in part one of my lectures, a representative collection of models for the equation of state of superdense neutron star matter, which account for various…

Astrophysics · Physics 2007-05-23 Fridolin Weber , Norman K. Glendenning

We investigate the properties of fermion-boson stars (FBSs), which can be viewed as neutron stars with a bosonic dark matter (DM) admixture. A challenge in studying the impact of DM on neutron stars is the absence of a universally accepted…

High Energy Astrophysical Phenomena · Physics 2025-10-21 Kelvin Ka-Ho Lam , Lap-Ming Lin

We investigate boson stars within the framework of the self-interacting Einstein-Friedberg-Lee-Sirlin (E-FLS) model, constituted by a complex scalar field with a quartic self-interaction and a real scalar field. Our analysis explores the…

General Relativity and Quantum Cosmology · Physics 2025-11-25 Pedro L. Brito de Sá , Haroldo C. D. Lima , Carlos A. R. Herdeiro , Luís C. B. Crispino

Scalar particles are a common prediction of many beyond the Standard Model theories. If they are light and cold enough, there is a possibility they may form Bose-Einstein condensates, which will then become gravitationally bound. These…

Cosmology and Nongalactic Astrophysics · Physics 2016-10-19 Eric Cotner

A simple model to study boson stars is to consider these stellar objects as quantum systems of $N$ identical self-gravitating particles within a non-relativistic framework. Some results obtained with point-like particles are recalled as…

High Energy Astrophysical Phenomena · Physics 2017-04-25 C. Semay

We present an exhaustive analysis of the numerical evolution of the Einstein-Klein-Gordon equations for the case of a real scalar field endowed with a quadratic self-interaction potential. The self-gravitating equilibrium configurations are…

General Relativity and Quantum Cosmology · Physics 2009-11-10 Miguel Alcubierre , Ricardo Becerril , F. Siddhartha Guzman , Tonatiuh Matos , Dario Nunez , L. Arturo Urena-Lopez

Bosonic stars,hypothetical astrophysical entities, are generally categorized into two primary classes based on the nature of their constituent particles: Einstein Klein Gordon stars, made up of massive scalar bosons, and Proca stars, their…

Astrophysics of Galaxies · Physics 2025-09-24 Jorge Castelo Mourelle , Nicolas Sanchis-Gual , José A. Font

We study Einstein-Yang-Mills equations in the presence of gravitating non-topological soliton field configurations, of q-ball type. We produce numerical solutions, stable with respect to gravitational collapse and to fission into free…

High Energy Physics - Theory · Physics 2009-11-10 Athanasios Prikas

In the present work we consider the existence and stability of Einstein static {\sf ES} Universe in Brans-Dicke ({\sf BD}) theory with non-vanishing spacetime torsion. In this theory, torsion field can be generated by the {\sf BD} scalar…

General Physics · Physics 2019-03-26 Hamid Shabani , Amir Hadi Ziaie

A model of static boson-fermion star with spherical symmetry based on the scalar-tensor theory of gravity with massive dilaton field is investigated numerically. Since the radius of star is \textit{a priori} an unknown quantity, the…

Numerical Analysis · Mathematics 2025-10-20 T. L. Boyadjiev , M. D. Todorov , P. P. Fiziev , S. S. Yazadjiev