标题： 动态空洞被冲击的常规多态气体包层包围 显示英文标题

标题： Dynamic Voids Surrounded by Shocked Conventional Polytropic Gas Envelopes

摘要： 在自引力多级气体球周围适当的能量和动量输入物理机制下，中心可能会出现一个质量含量非常少的中心球形“空腔”或“凹陷”或“气泡”，然后动态地扩展进入各种质量更大的周围气体包层，可能伴有激波。我们研究了具有这种扩展“空腔”的自引力多级流体动力学流动的自相似演化。空腔边界支撑着一个质量包层，这是一个压力平衡的接触间断面，质量密度和温度在此发生剧烈变化。我们获得了可以平滑或通过激波穿越声学临界面的数值空腔解。使用传统的多级状态方程，我们构建了包含静态多级球体、流出、流入、微风和收缩类型的多种包层中传播激波的全局空腔解。在超新星的背景下，我们讨论了通过动态扩展的强大空腔将中心坍缩致密天体与向外气体包层分离的可能情景。最初，一个中心气泡由极其强大的中微子层雕刻出来。在中微子脱耦后，强电磁辐射场和/或电子-正电子对等离子体继续驱动空腔的膨胀。在自相似的动力学演化中，接触间断面处的压力随时间减少到可忽略的水平，最终气体包层继续以惯性扩展。我们描述了多项式指数为$\gamma=4/3-\epsilon$且具有$\epsilon>0$的模型案例，并讨论了证明我们提出的情景的相关要求。 显示英文摘要

摘要： With proper physical mechanisms of energy and momentum input from around the centre of a self-gravitating polytropic gas sphere, a central spherical "void" or "cavity" or "bubble" of very much less mass contents may emerge and then dynamically expand into a variety of surrounding more massive gas envelopes with or without shocks. We explore self-similar evolution of a self-gravitating polytropic hydrodynamic flow of spherical symmetry with such an expanding "void" embedded around the center. The void boundary supporting a massive envelope represents a pressure-balanced contact discontinuity where drastic changes in mass density and temperature occur. We obtain numerical void solutions that can cross the sonic critical surface either smoothly or by shocks. Using the conventional polytropic equation of state, we construct global void solutions with shocks travelling into various envelopes including static polytropic sphere, outflow, inflow, breeze and contraction types. In the context of supernovae, we discuss the possible scenario of separating a central collapsing compact object from an outgoing gas envelope with a powerful void in dynamic expansion. Initially, a central bubble is carved out by an extremely powerful neutrinosphere. After the escape of neutrinos during the decoupling, the strong electromagnetic radiation field and/or electron-positron pair plasma continue to drive the cavity expansion. In a self-similar dynamic evolution, the pressure across the contact discontinuity decreases with time to a negligible level for a sufficiently long lapse and eventually, the gas envelope continues to expand by inertia. We describe model cases of polytropic index $\gamma=4/3-\epsilon$ with $\epsilon>0$ and discuss pertinent requirements to justify our proposed scenario.