MURCA驱动的中微子陷俘重子物质中的体粘滞
MURCA driven Bulk viscosity in neutrino trapped baryonic matter
AI总结：
在双中子星并合背景下，采用NL3和DDME2模型研究含陷俘中微子重子物质的体粘滞，发现中微子使体粘滞峰值偏移，粘滞衰减时间尺度为32-100毫秒，与残骸存活时间一致。
摘要：
我们在双中子星并合的背景下，研究了考虑重子物质中陷俘中微子的体粘滞。并合事件发生后，双星可产生密度高达$5$倍核饱和密度、温度高达$50$ MeV的致密残骸天体，导致中微子被保留。我们采用两个相对论平均场模型（NL3和DDME2）来描述中微子陷俘重子物质。耗散系数通过评估致密重子介质中的Modified URCA相互作用速率，并考虑密度振荡引起的扰动来确定。我们观察到体粘滞随介质温度变化时的共振行为。体粘滞峰值保持在$\sim 13-50$ MeV的温度范围内，具体取决于底层状态方程和轻子分数。该温度范围对应于双中子星并合的相关区域。我们还注意到，在介质中存在中微子时，体粘滞峰值向更高温度偏移，且体粘滞峰值也发生变化。粘滞耗散的时间尺度由核状态方程导出的beta偏离平衡磁化率决定。由此产生的粘滞衰减时间尺度范围为$32-100$毫秒，这与特定场景下并合后天体的存活时间在数量级上保持一致。
英文摘要：
We examine bulk viscosity, taking into account trapped neutrinos in baryonic matter, in the context of binary neutron star mergers. Following the merging event, the binary star can yield a remnant compact object with densities up to $5$ nuclear saturation density and temperature upto $50$ MeV resulting in the retention of neutrinos. We employ two relativistic mean field models, NL3 and DDME2, to describe the neutrino-trapped baryonic matter. The dissipation coefficient is determined by evaluating the Modified URCA interaction rate in the dense baryonic medium, and accounting for perturbations caused by density oscillations. We observe the resonant behavior of bulk viscosity as it varies with the temperature of the medium. The bulk viscosity peak remains within the temperature range of $\sim 13-50$ MeV, depending upon the underlying equation of states and lepton fractions. This temperature range corresponds to the relevant domain of binary neutron star mergers. We also note that in presence of neutrinos in the medium the bulk viscosity peak shifts towards higher temperature and the peak value of bulk viscosity also changes. The time scale of viscous dissipation is dictated by the beta-off-equilibrium susceptibilities derived from the nuclear equation of state. The resulting viscous decay time scale ranges from $32-100$ milliseconds, which aligns with the order of magnitude of the post-merger object's survival time in some specific scenarios.
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