Fragmentation of neutron star matter

P ALCAIN; C. O. DORSO

INTERNATIONAL JOURNAL OF MODERN PHYSICS E-NUCLEAR PHYSICS

WORLD SCIENTIFIC PUBL CO PTE LTD

Lugar: London, UK; Año: 2017

0218-3013

Background: Neutron stars are astronomical systems with nucleons submitted to extreme conditions. Due tothe long range coulomb repulsion between protons, the system has structural inhomogeneities. These structuralinhomogeneities arise also in expanding systems, where the fragment distribution is highly dependent on thethermodynamical conditions (temperature, proton fraction, . . . ) and the expansion velocity.Purpose: We aim to find the different regimes of fragment distribution, and the existence of infinite clusters.Method: We study the dynamics of the nucleons with a semiclassical molecular dynamics model. Starting withan equilibrium configuration, we expand the system homgeneously until we arrive to an asymptotical configuration(i. e. very low final densities). We study the fragment distribution throughout this expansion.Results: We found the typical regimes of the asymptotical fragment distribution of an expansion: u-shaped,power law and exponential. Another key feature in our calculations is that, since the interaction between protonsis long range repulsive, we do not have always an infinite fragment. We found that, as expected, the faster theexpansion velocity is, the quicker the infinite fragment disappears.Conclusions: We have developed a graph-based tool for the identification of infinite fragments, and found atransition from U-shaped to exponential fragment mass distribution with increasing expansion rate.