Numerical simulation of the hydrodynamical combustion to strange quark matter in the trapped neutrino regime

Abstract

We simulate and study the microphysics of combustion (flame burning) of two flavored quark matter (u, d) to three flavoured quark matter (u,d,s) in a trapped neutrino regime applicable to conditions prevailing in a hot proto-neutron star. The reaction-diffusion-advection equations for (u,d) to (u,d,s) combustion are coupled with neutrino transport, which is modelled through a flux-limited diffusion scheme. The flame speed is proportional to initial lepton fraction because of the release of electron chemical potential as heat, and reaches a steady-state burning speed of (0.001-0.008)c. We find that the burning speed is ultimately driven by the neutrino pressure gradient, given that the pressure gradient induced by quarks is opposed by the pressure gradients induced by electrons. This suggests, somewhat counter-intuitively, that the pressure gradients that drive the interface are controlled primarily by leptonic weak decays rather than by the quark Equation of State (EOS). In other words, the effects of the leptonic weak interaction, including the corresponding weak decay rates and the EOS of electrons and neutrinos, are at least as important as the uncertainties related to the EOS of high density matter. We find that for baryon number densities n B ≤ 0.35 fm −3 , strong pressure gradients induced by leptonic weak decays drastically slow down the burning speed, which is thereafter controlled by the much slower burning process driven by backflowing downstream matter. We discuss the implications of our findings to proto-neutron stars.

Gravitational wave echoes from strange stars

“…The formation of a strange star would certainly be accompanied by a release of energy, as discussed in framework of supernova explosions, see for example [26][27][28], possibly affecting the gamma and neutrino emissions associated to the merging of NSs. The GW post merger emission could also be different, but we are not aware of any simulation of merging of NSs leading to the formation of a strange star.…”

Hadron–Quark Combustion as a Nonlinear, Dynamical System

“…In fact, they found, by solving the semi-analytic, hydrodynamic jump conditions, that, for a given neutrino cooling rate, thermal pressure gradients could slow down the combustion front by orders of magnitude. Ouyed et al [17] (hereby Paper II) later confirmed this initial intuition numerically, by incorporating neutrino transport and electron pressure into the reaction-diffusionadvection equations. The authors of Paper II discovered that feedback effects triggered by various leptonic processes could affect the burning timescale by orders of magnitude.…”

The Structure of the Hadron-Quark Combustion Zone

“…Later on, Ouyed et al [18] explored the effect of neutrinos in the interface by implementing a neutrino diffusion scheme and including neutrinos and electrons in the EOS. They found that indeed, neutrinos can cause the interface to halt.…”

“…In other words, including the dynamical effects of the reaction zone can lead to counter-intuitive behavior such as quenching due to time-dependent effects, which are not captured when using the steady state solutions of Olinto or the jump-conditions [18,17].…”

“…2 is whether combustion can proceed since neutrino absorption introduces an energy barrier. However, one has to keep in mind that the neutrino absorption used here is done under the approximation of trapped neutrinos [18]. In reality, matter is only semi-opaque in the reaction zone to neutrinos, since the mean free Hadronic matter deconfines to 2QM through the strong interaction, while 2QM decays to 3QM through the nonleptonic process d → s (for the case of deleptonized matter, otherwise there are leptonic processes as well).…”