arXiv subjects

Jerome Novak

Publications and source records attributed to Jerome Novak.

21 records · Page 2Linked to original sources

arXiv2003

Gyromagnetic ratio of rapidly rotating compact stars in general relativity

We numerically calculate equilibrium configurations of uniformly rotating and charged neutron stars, in the case of insulating material and neglecting the electromagnetic forces acting on the equilibrium of the fluid. This allows us to study the behaviour of the gyromagnetic ratio for those objects, when varying rotation rate and equation of state for the matter. Under the assumption of low charge and incompressible fluid, we find that the gyromagnetic ratio is directly proportional to the compaction parameter M/R of the star, and very little dependent on its angular velocity. Nevertheless, it seems impossible to have g=2 for these models with low charge-to-mass ratio, where matter consists of a perfect fluid and where the collapse limit is never reached.

gr-qc↗

arXiv2001

Velocity-induced collapses of stable neutron stars

The collapse of spherical neutron stars is studied in General Relativity. The initial state is a stable neutron star to which an inward radial kinetic energy has been added through some velocity profile. For two different equations of state and two different shapes of velocity profiles, it is found that neutron stars can collapse to black holes for high enough inward velocities, provided that their masses are higher than some minimal value, depending on the equation of state. For a polytropic equation of state of the form $p=Kρ^γ$, with $γ= 2$ it is found to be $1.16 (\frac{K}{0.1})^{0.5} \msol$, whereas for a more realistic one, it reads $0.36 \msol $. In some cases of collapse forming a black hole, part of the matter composing the initial neutron star can be ejected through a shock, leaving only a fraction of the initial mass to form a black hole. Therefore, black holes of very small masses can be formed and, in particular, the mass scaling relation, as a function of initial velocity, takes the form discovered by Choptuik for critical collapses.

gr-qc↗

arXiv2001

Numerical Relativity CM1-a and CM1-b sessions

Numerical Relativity is concerned with solving the Einstein equations, as well as any field or matter equations on curved space-time, by means of computer calculations. The methods developed for this purpose up to now, as well as the addressed physical problems are getting more numerous every day. This is a brief summary of the presentations which have been given during the 9th Marcel Grossman meeting, which took place in Rome, from 2nd to 8th of July 2000. Many different fields have been addressed, from pure numerics and applied mathematics to neutron star properties and gravitational wave astronomy.

gr-qc↗