Speaker
Dr
Luca Franci
(Università di Parma)
Description
We present numerical results on the dynamical bar-mode (m=2)
instability in differentially rotating relativistic star models with a
polytropic EoS, obtained by means of full 3D ideal
magneto-hydrodynamics simulations in full General Relativity. We
focus our attention on two different ingredients that may affect the
onset and the dynamics of the instability, i.e., the magnetization and
the stiffness of the EoS. The first study is carried out by
superimposing to initial (matter) equilibrium configurations purely
poloidal magnetic fields of different strength (in the range
$10^{12}$-$10^{16}$ Gauss). We find that magnetic fields of order
$10^{15}$ Gauss or less have negligible effects on bar-mode unstable
models, while stronger magnetic fields are able to completely suppress
the hydrodynamic instability which is present in the unmagnetized
case. The second study is carried out by changing the adiabatic index
of the polytropic EoS from 2 to 2.75, in order to mimic the behavior
of a realistic EoS. We determine the change on the threshold for the
emergence of the instability. We also extend the analysis to low
values of the instability parameter \beta to check for the presence of
low-\beta or shear instabilities.
Author
Dr
Luca Franci
(Università di Parma)
