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The discovery of a 2 Msun neutron star provided a robust constraint for the theory of exotic dense matter, bringing into question the existence of strange baryons in the interiors of neutron stars. Although many theories fail to reproduce…

Solar and Stellar Astrophysics · Physics 2013-03-26 M. Bejger

We continue to investigate various instabilities of the fixed backgrounds related to the de Sitter space. It is shown that in many cases the in/in perturbation theory contains IR/UV mixing and thus is non-renormalizible. The application of…

High Energy Physics - Theory · Physics 2012-09-20 A. M. Polyakov

This paper is a mixture of expository material and current research material. Among new results are examples of generalised harmonic spinors and their gauged version, the generalised Seiberg-Witten equations.

Differential Geometry · Mathematics 2015-11-05 Andriy Haydys

General relativistic cosmology cannot be reduced to linear relativistic perturbations superposed on an isotropic and homogeneous (Friedmann-Robertson-Walker) background, even though such a simple scheme has been successfully applied to…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-22 Eleonora Villa , Licia Verde , Sabino Matarrese

The universal relationships for compact stars have been investigated employing perturbative approach using canonical (APR) and Brussels-Montreal Skyrme (BSk22, BSk24, BSk26) equations of state describing hadronic matter of neutron stars.…

Nuclear Theory · Physics 2024-08-02 Debasis Atta , Vinay Singh , D. N. Basu

We present a code to construct initial data for binary neutron star systems in which the stars are rotating. Our code, based on a formalism developed by Tichy, allows for arbitrary rotation axes of the neutron stars and is able to achieve…

The extension of Dirac's LNH to cover cosmological and fine-structure time-varying "constants", and the rotation of the Universe, is here analysed, including a "derivation" of the angular speed of the present Universe, and of the…

General Physics · Physics 2013-02-19 Marcelo Samuel Berman

A new spectral code for constructing general-relativistic models of rapidly rotating stars with an unprecedented accuracy is presented. As a first application, we reexamine uniformly rotating homogeneous stars and compare our results with…

Astrophysics · Physics 2010-12-23 M. Ansorg , A. Kleinwächter , R. Meinel

Recent developments in neutron star theory and observation are discussed. Based on modern nucleon-nucleon potentials more reliable equations of state for dense nuclear matter have been constructed. Furthermore, phase transitions such as…

Nuclear Theory · Physics 2010-11-19 H. Heiselberg

Five classes of radiative solutions of Einstein's field equations are discussed in the light of some new developments. These are plane waves and their collisions, cylindrical waves, Robinson-Trautman and type N spacetimes, boost-rotation…

General Relativity and Quantum Cosmology · Physics 2017-09-27 Jiri Bicak

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

In this paper, we investigate the geometry of Einstein-type equation on a Riemannian manifold, unifying various particular geometric structures recently studied in the literature, such as critical point equation and vacuum static equation.…

Differential Geometry · Mathematics 2022-03-31 Gabjin Yun , Seungsu Hwang

Irrotational dust solutions of Einstein's equations are suitable models to describe the general-relativistic aspects of the gravitational instability mechanism for the formation of cosmic structures. In this paper we study their state space…

General Relativity and Quantum Cosmology · Physics 2009-11-07 Carlos F. Sopuerta

The purpose of this article is to draw attention to some fundamental issues in General Relativity. It is argued that these deep issues cannot be resolved within the standard approach to general relativity that considers {\em every} solution…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Sanjay M. Wagh

The non-linear behaviour of oscillation modes in compact stars is a topic of considerable current interest. Accurate numerical studies of such phenomena are likely to require powerful new approaches to both fluid and spacetime computations.…

Astrophysics · Physics 2007-05-23 Uli Sperhake , Philippos Papadopoulos , Nils Andersson

We introduce new times in the monodromy preserving equations. While the usual times related to the moduli of complex structures of Riemann curves such as coordinates of marked points, we consider the moduli of generalized complex structures…

Exactly Solvable and Integrable Systems · Physics 2007-05-23 M. Olshanetsky

In this paper we review the basics of magneto-rotational properties of neutron stars focusing on spin-up/spin-down behavior at different evolutionary stages. The main goal is to provide equations for the spin frequency changes in various…

High Energy Astrophysical Phenomena · Physics 2024-02-08 P. Abolmasov , A. V. Biryukov , S. B. Popov

We consider the dependence of the internal structure of a neutron star in a close binary system on the semi-major axis of the binary orbit, focusing on the case when the Roche lobes of the components are nearly filled. We adopt a polytropic…

Astrophysics · Physics 2007-05-23 O. A. Kuznetsov , M. E. Prokhorov , M. V. Sazhin , V. M. Chechetkin

We present the field equations governing the equilibrium of rapidly rotating neutron stars in scalar-tensor theories of gravity, as well as representative numerical solutions. The conditions for the presence of a nontrivial scalar field and…

General Relativity and Quantum Cosmology · Physics 2014-02-25 Daniela D. Doneva , Stoytcho S. Yazadjiev , Nikolaos Stergioulas , Kostas D. Kokkotas

We present new results for pulsating stars in general relativity. First we show that the so-called gravitational-wave modes of a neutron star can be excited when a gravitational wave impinges on the star. Numerical simulations suggest that…

General Relativity and Quantum Cosmology · Physics 2009-10-28 Nils Andersson , Kostas D. Kokkotas