The frozen star is a nonsingular, ultracompact object that, to an external observer, looks exactly like a Schwarzschild black hole, but with a different interior geometry and matter composition. The frozen star needs to be sourced by an extremely anisotropic fluid, for which the sum of the radial pressure and energy density is either vanishing or perturbatively small. Here, we show that this matter can be identified with the string fluid resulting from the decay of an unstable 𝐷-brane or a brane-antibrane system at the end of open-string tachyon condensation. The string fluid corresponds to flux tubes emanating from the center and ending at the Schwarzschild radius of the star. The effective Lagrangian for this fluid can be recast into a Born-Infeld form. When the fluid Lagrangian is coupled to that of Einstein’s gravity, the static, spherically symmetric solutions of the equations of motion are shown to be the same as those describing the frozen star model. Frozen stars can therefore be viewed as a gravitationally backreacted BIons model or that of gravitationally confined flux tubes. The Born-Infeld Lagrangian provides a complete set of equations that describe the dynamics of the frozen star in a generic state, which is not necessarily static nor spherically symmetric. Our framework therefore should allow a fully dynamical and out-of-equilibrium description of the frozen star model which will be relevant to gravitational waves observations of mergers of astrophysical black holes.

中文翻译：

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冰冻恒星：由弦状流体产生的黑洞模拟物


这颗冰冻的恒星是一个非奇异的超致密天体，在外部观察者看来，它看起来与史瓦西黑洞一模一样，但内部几何形状和物质组成不同。冰冻的恒星需要来自极度各向异性的流体，对于这种流体，径向压力和能量密度之和要么消失，要么微小。在这里，我们表明，这种物质可以用开弦速子凝结结束时不稳定的 D-brane 或 brane-antibrane 系统衰变产生的串流体来识别。串流体对应于从中心发出并在恒星的 Schwarzschild 半径处结束的磁通管。这种流体的有效拉格朗日可以重铸为 Born-Infeld 形式。当流体拉格朗日与爱因斯坦引力耦合时，运动方程的静态球对称解与描述冻结恒星模型的解相同。因此，冻结的恒星可以被视为引力反反应的 BIons 模型或引力限制磁通管的模型。Born-Infeld 拉格朗日方程提供了一套完整的方程，这些方程描述了冰冻恒星在一般状态下的动力学，这种状态不一定是静态的，也不一定是球对称的。因此，我们的框架应该允许对冻结的恒星模型进行完全动力学和不平衡的描述，这将与天体物理黑洞合并的引力波观测有关。