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The paper provides a new framework for the description of linearized adiabatic lagrangian perturbations and stability of differentially rotating newtonian stars. In doing so it overcomes problems in a previous framework by Dyson and Schutz…

Astrophysics · Physics 2014-10-13 Horst R. Beyer

Stars may be understood as self-gravitating masses of a compressible fluid whose radiative cooling is compensated by nuclear reactions or gravitational contraction. The understanding of their time evolution requires the use of detailed…

Solar and Stellar Astrophysics · Physics 2016-06-22 M. Rieutord , F. Espinosa Lara , B. Putigny

This work focuses on the study of solitary wave solutions to a nonlocal, nonlinear Schr\"odinger system in $1$+$1$ dimensions with arbitrary nonlinearity parameter $\kappa$. Although the system we study here was first reported by Yang…

Pattern Formation and Solitons · Physics 2021-05-03 Efstathios G. Charalampidis , Fred Cooper , Avinash Khare , John F. Dawson , Avadh Saxena

The basic formulation describing quadratic mode coupling in rotating Newtonian stars is presented, focusing on polar modes. Due to the Chandrasekhar-Friedman-Schutz mechanism, the f-mode (fundamental oscillation) is driven unstable by the…

High Energy Astrophysical Phenomena · Physics 2015-12-29 Pantelis Pnigouras , Kostas D. Kokkotas

In this paper Einstein's field equations, for static spherically symmetric perfect fluid models with a linear barotropic equation of state, are recast into a 3-dimensional regular system of ordinary differential equations on a compact state…

General Relativity and Quantum Cosmology · Physics 2009-10-31 U. S. Nilsson , C. Uggla

We demonstrate how observables of slowly rotating neutron stars can be used to constrain the nuclear equation of state. By building a Bayesian framework we demonstrate how combining different types of neutron star measurements, motivated by…

General Relativity and Quantum Cosmology · Physics 2022-07-20 Sebastian H. Völkel , Christian J. Krüger

Most numerical models of binary stars - in particular neutron stars in compact binaries - assume the companions to be either corotational or irrotational. Either one of these assumptions leads to a significant simplification in the…

General Relativity and Quantum Cosmology · Physics 2009-10-02 Thomas W. Baumgarte , Stuart L. Shapiro

Neutron stars provide a natural laboratory for studying the properties of dense nuclear matter under extreme conditions. In this proceeding, we review our current understanding of dense isospin symmetric and asymmetric matter and neutron…

Nuclear Theory · Physics 2025-04-01 Rajesh Kumar , Veronica Dexheimer , Johannes Jahan

We introduce a Newtonian model for the deformations of a compressible, autogravitating, and continuously stratified neutron star. The present framework can be applied to a number of astrophysical scenarios as it allows us to account for a…

High Energy Astrophysical Phenomena · Physics 2020-01-15 Elia Giliberti , Gabriele Cambiotti , Marco Antonelli , Pierre Pizzochero

We investigate the nature of low T/W dynamical instabilities in various ranges of the stiffness of the equation of state in differentially rotating stars. Here T is the rotational kinetic energy, while W the gravitational binding energy. We…

High Energy Astrophysical Phenomena · Physics 2018-07-05 Motoyuki Saijo

Many challenging tasks in sensor networks, including sensor calibration, ranking of nodes, monitoring, event region detection, collaborative filtering, collaborative signal processing, {\em etc.}, can be formulated as a problem of solving a…

Distributed, Parallel, and Cluster Computing · Computer Science 2008-11-21 Ezra N. Hoch , Danny Bickson , Danny Dolev

It was recently shown, that in a class of tensor-multi-scalar theories of gravity with a nontrivial target space metric, there exist scalarized neutron star solutions. An important property of these compact objects is that the scalar charge…

General Relativity and Quantum Cosmology · Physics 2021-12-15 Hao-Jui Kuan , Jasbir Singh , Daniela D. Doneva , Stoytcho S. Yazadjiev , Kostas D. Kokkotas

Evolution of scalar perturbations in a universe containing solid matter with positive pressure is studied. Solution for pure solid is found and matched with solution for ideal fluid, including the case when the pressure to energy density…

General Relativity and Quantum Cosmology · Physics 2015-01-29 Vladimír Balek , Matej Škovran

A novel numerical method for solving inverse scattering problem with fixed-energy data is proposed. The method contains a new important concept: the stability index of the inversion problem. This is a number, computed from the data, which…

Mathematical Physics · Physics 2007-05-23 S. Gutman , A. G. Ramm , W. Scheid

It is well known that a fixed point iteration for solving a linear equation system converges if and only if the spectral radius of the iteration matrix is less than one. A method is presented which guarantees the Fixed Point, even if this…

Numerical Analysis · Computer Science 2020-12-22 Hubert Karl , Sebstian Karl

We systematically extend the statement that the configurational entropy provides an alternative approach to studying gravitational stability of compact objects, carried out in the previous work of M. Gleiser and N. Jiang, Phys. Rev. D {\bf…

General Relativity and Quantum Cosmology · Physics 2023-03-20 P. S. Koliogiannis , G. A. Tsalis , C. P. Panos , Ch. C. Moustakidis

We present results about the effect of the use of a stiffer equation of state, namely the ideal-fluid $\Gamma=2.75$ ones, on the dynamical bar-mode instability in rapidly rotating polytropic models of neutron stars in full General…

General Relativity and Quantum Cosmology · Physics 2014-07-16 Roberto De Pietri , Alessandra Feo , Luca Franci , Frank Löffler

Models of neutron stars are considered in the case of a uniform density distribution. An algebraic equation, valid for any equation of state, is obtained. This equation allows one to find the approximate mass of a star of a given density…

High Energy Astrophysical Phenomena · Physics 2023-11-14 G. S. Bisnovatyi-Kogan , E. A. Patraman

We investigate close binary neutron stars in quasiequilibrium states in a general relativistic framework. We assume conformal flatness for the spatial metric and irrotational velocity field for the neutron stars. We adopt the polytropic…

General Relativity and Quantum Cosmology · Physics 2009-10-31 Koji Uryu , Masaru Shibata , Yoshiharu Eriguchi

The development of an analytically iterative method for solving steady-state as well as unsteady-state problems of cosmic-ray (CR) modulation is proposed. Iterations for obtaining the solutions are constructed for the spherically symmetric…

Instrumentation and Methods for Astrophysics · Physics 2017-07-04 Yuriy L. Kolesnyk , Pavol Bobik , Boris A. Shakhov , Marian Putis