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Several computer codes based on phenomenological models are being developed with the aim of obtaining fission observables, such as neutron and gamma multiplicities and product yields. Key points in these calculations, which are handled…

A new two dimensional non-perturbative code to compute accurate oscillation modes of rapidly rotating stars is presented. The 2D calculations fully take into account the centrifugal distorsion of the star while the non perturbative method…

Solar and Stellar Astrophysics · Physics 2013-01-14 R-M. Ouazzani , I. W. Roxburgh , M-A Dupret

The construction of accurate and consistent initial data for various binary parameters is a critical ingredient for numerical relativity simulations of the compact binary coalescence. In this article, we present an upgrade of the…

General Relativity and Quantum Cosmology · Physics 2019-12-25 Wolfgang Tichy , Alireza Rashti , Tim Dietrich , Reetika Dudi , Bernd Brügmann

Quantifying inherent neutron sources in matter, particularly $(\alpha, n)$ reactions and spontaneous fission, is important in nuclear engineering and other fields. The SOURCES code is a common tool for calculating the yield and spectrum of…

Nuclear Theory · Physics 2025-10-28 Sigtryggur Hauksson , Ilaria Casalbore , Daniele Tomatis , Nunzio Burgio

Using time evolutions of the relevant linearised equations we study non-axisymmetric oscillations of rapidly rotating and superfluid neutron stars. We consider perturbations of Newtonian axisymmetric background configurations and account…

Astrophysics · Physics 2009-11-13 Andrea Passamonti , Brynmor Haskell , Nils Andersson

A binary neutron star merger produces a rapidly and differentially rotating compact remnant whose lifespan heavily affects the electromagnetic and gravitational emissions. Its stability depends on both the equation of state (EOS) and the…

General Relativity and Quantum Cosmology · Physics 2017-12-27 Gabriele Bozzola , Nikolaos Stergioulas , Andreas Bauswein

A new method is described for constructing initial data for a binary neutron-star (BNS) system in quasi-equilibrium circular orbit. Two formulations for non-conformally flat data, waveless (WL) and near-zone helically symmetric (NHS), are…

General Relativity and Quantum Cosmology · Physics 2013-05-29 Koji Uryu , Francois Limousin , John L. Friedman , Eric Gourgoulhon , Masaru Shibata

To date, essentially all simulation codes that solve the full set of Einstein's equations are performed in the framework of Eulerian hydrodynamics. The exception is our recently developed Numerical Relativity code SPHINCS_BSSN which solves…

General Relativity and Quantum Cosmology · Physics 2022-06-17 S. Rosswog , P. Diener , F. Torsello

We have developed a new numerical scheme to solve r-mode oscillations of {\it rapidly rotating polytropic stars} in Newtonian gravity. In this scheme, Euler perturbations of the density, three components of the velocity are treated as four…

Astrophysics · Physics 2009-10-31 Shigeyuki Karino , Shin'ichirou Yoshida , Shijun Yoshida , Yoshiharu Eriguchi

We study time evolutions of superfluid neutron stars, focussing on the nature of the oscillation spectrum, the effect of mutual friction force on the oscillations and the hydrodynamical spin-up phase of pulsar glitches. We linearise the…

Solar and Stellar Astrophysics · Physics 2015-05-18 A. Passamonti , N. Andersson

We study the solution space of general relativistic, axisymmetric, equilibria of differentially rotating neutron stars with realistic, nuclear equations of state. We find that different types of stars, which were identified by earlier works…

High Energy Astrophysical Phenomena · Physics 2019-05-08 Pedro Espino , Vasileios Paschalidis

In the mathematical physics literature, there are heuristic arguments, going back three decades, suggesting that for an open set of initially smooth solutions to the Einstein-vacuum equations in high dimensions, stable, approximately…

Analysis of PDEs · Mathematics 2018-04-19 Igor Rodnianski , Jared Speck

We construct equilibrium configurations for neutron stars using a specific $f(R,T)$ functional form, recently derived through gaussian process applied to measurements of the Hubble parameter. By construction, this functional form serves as…

General Relativity and Quantum Cosmology · Physics 2024-11-15 J. T. Quartuccio , P. H. R. S. Moraes , G. N. Zeminiani , M. M. Lapola

(Abridged) Numerical simulation of strange quark stars (QSs) is challenging due to the strong density discontinuity at the stellar surface. In this paper, we report successful simulations of rapidly rotating QSs and study their oscillation…

General Relativity and Quantum Cosmology · Physics 2023-09-08 Kenneth Chen , Lap-Ming Lin

We present a new code, named COCAL - Compact Object CALculator, for the computation of equilibriums and quasiequilibrium initial data sets of single or binary compact objects of all kinds. In the cocal code, those solutions are calculated…

General Relativity and Quantum Cosmology · Physics 2013-05-30 Koji Uryu , Antonios Tsokaros

Information about the last stages of a binary neutron star inspiral and the final merger can be extracted from quasi-equilibrium configurations and dynamical evolutions. In this article, we construct quasi-equilibrium configurations for…

We study equilibrium sequences of close binary systems composed of identical polytropic stars in Newtonian gravity. The solving method is a multi-domain spectral method which we have recently developed. An improvement is introduced here for…

General Relativity and Quantum Cosmology · Physics 2009-11-07 Keisuke Taniguchi , Eric Gourgoulhon , Silvano Bonazzola

We study the application of the generalized convolution quadrature (gCQ) based on Runge--Kutta methods to approximate the solution of an important class of sectorial problems. The gCQ generalizes Lubich's original convolution quadrature…

Numerical Analysis · Mathematics 2025-06-27 Jing Guo , Maria Lopez-Fernandez

We study the axial (or odd-parity) perturbations of neutron stars in a one-parameter subclass of Degenerate Higher-Order Scalar-tensor (DHOST) theories. After recalling the equilibrium neutron star configurations obtained in a previous work…

General Relativity and Quantum Cosmology · Physics 2025-07-04 Hamza Boumaza , David Langlois

In this paper we present a new approach to the inverse problem for relativistic stars using quasinormal modes and the piecewise polytropic parametrization of the equation of state. The algorithm is a piecewise polytropic meshing and…

General Relativity and Quantum Cosmology · Physics 2019-05-10 Juan Mena-Fernández , Luis Manuel González-Romero