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arXiv 1902.01468gr-qcastro-ph.COhep-th
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Horndeski理论中球引力坍缩的双曲性

Hyperbolicity in Spherical Gravitational Collapse in a Horndeski Theory

Justin L Ripley, Frans Pretorius

摘要:

数值研究了平移对称Einstein-Gauss-Bonnet(EdGB)引力场中的球形引力坍缩.我们发现的证据表明,有开放的初始数据集的字符的方程组的变化从双曲型到椭圆型的时空的紧凑区域。在这些情况下,系统的演变,作为一个双曲型的初边值问题,导致运动方程成为不适定的椭圆形区域的形式。在相应的有效“柯西视界”上没有遇到奇点或间断。因此,可以想象,如果方程被适当地处理为混合型,那么EdGB引力的适定公式(至少在球对称范围内)是可能的。

英文摘要:

We numerically study spherical gravitational collapse in shift symmetric Einstein dilaton Gauss Bonnet (EdGB) gravity. We find evidence that there are open sets of initial data for which the character of the system of equations changes from hyperbolic to elliptic type in a compact region of the spacetime. In these cases evolution of the system, treated as a hyperbolic initial boundary value problem, leads to the equations of motion becoming ill-posed when the elliptic region forms. No singularities or discontinuities are encountered on the corresponding effective "Cauchy horizon". Therefore it is conceivable that a well-posed formulation of EdGB gravity (at least within spherical symmetry) may be possible if the equations are appropriately treated as mixed-type.

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