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arXiv 1811.04487gr-qchep-th
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没有Gauss-Bonnet物质耦合的四阶Gauss-Bonnet引力-球对称解、畴壁和时空奇点

Four-Dimensonal Gauss-Bonnet Gravity Without Gauss-Bonnet Coupling to Matter - Spherically Symmetric Solutions, Domain Walls and Spacetime Singularities

Eduardo Guendelman, Emil Nissimov, Svetlana Pacheva

摘要:

我们讨论了一个新的扩展的引力模型在普通的$D=4$时空维,其中一个额外的条款,在涉及高斯-邦尼拓扑密度的行动,而不需要耦合到物质场不同于普通的D=4高斯-邦尼重力模型的情况下。避免高斯-博内密度成为全导数是通过采用度量独立的非黎曼时空体积形式的形式来实现的。非黎曼体积元动态地触发高斯-博内标量成为壳层上的任意积分常数。我们详细地描述了上述修正的D=4 Gauss-Bonnet引力的静态球对称解,包括变形(反)-de Sitter几何、黑洞、畴壁和Kantowski-Sachs型宇宙的解.一些解显示出物理时空奇异表面,而不是隐藏在视界后面,并与整个空间禁区接壤。通过沿适当的畴壁成对匹配两个解,可以避免奇异性。对于一大类解,相应的物质源是一种特殊形式的非线性电动力学,其拉格朗日量L(F^2)是F^2(麦克斯韦张量F_mu_nu的平方)的非解析函数,即L(F^2)不是Born-Infeld型的。

英文摘要:

We discuss a new extended gravity model in ordinary $D=4$ spacetime dimensions, where an additional term in the action involving Gauss-Bonnet topological density is included without the need to couple it to matter fields unlike the case of ordinary D=4 Gauss-Bonnet gravity models. Avoiding the Gauss-Bonnet density becoming a total derivative is achieved by employing the formalism of metric-independent non-Riemannian spacetime volume-forms. The non-Riemannian volume element triggers dynamically the Gauss-Bonnet scalar to become an arbitrary integration constant on-shell. We describe in some detail the class of static spherically symmetric solutions of the above modified D=4 Gauss-Bonnet gravity including solutions with deformed (anti)-de Sitter geometries, black holes, domain walls and Kantowski-Sachs-type universes. Some solutions exhibit physical spacetime singular surfaces not hidden behind horizons and bordering whole forbidden regions of space. Singularities can be avoided by pairwise matching of two solutions along appropriate domain walls. For a broad class of solutions the corresponding matter source is shown to be a special form of nonlinear electrodynamics whose Lagrangian L(F^2) is a non-analytic function of F^2 (the square of Maxwell tensor F_mu_nu), i.e., L(F^2) is not of Born-Infeld type.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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