Disformal vectors and anisotropies on a warped brane\protect Hulluilla on Halvat Huvit
Disformal vectors and anisotropies on a warped brane\protect Hulluilla on Halvat Huvit
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DOI：
10.1088/1475-7516/2015/03/003
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发表时间：
2014-07
影响因子：
6.4
通讯作者：
T. Koivisto;F. Urban
中科院分区：
文献类型：
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作者：
T. Koivisto;F. Urban
麦克斯韦动作具有共形不变性，并且通常不知道共形平坦度量。然而，如果向量存在于非形式度量中（就像存在于移动膜上一样），则情况不再如此。然后，不规则耦合由狄拉克-玻恩-因菲尔德标量场介导。这里针对具有大量非形式耦合矢量场的各向异性 Bianchi I 宇宙学开发了系统动力系统分析。发现了几个新的固定点，包括各向异性缩放解。这里提出的形式主义可以方便地应用于有或没有额外维度动机的一般场景。这里通过执行完整的分析来说明这一点，假设膜的电势和扭曲因子都是（接近）指数的。在这种情况下，各向异性固定点要么不是吸引子，不能描述加速膨胀，要么它们的各向异性太大而与观测不兼容。尽管如此，仍然存在可行的模型类别，其中由于矢量场的快速振荡而保留了各向同性，从而提供了实现非形式相互作用的大量暗物质的可能。
The Maxwell action is conformally invariant and classically ignorant of conformally flat metrics. However, if the vector lives in a disformal metric—as it does if residing upon a moving brane—this is no longer true. The disformal coupling is then mediated by a Dirac-Born-Infeld scalar field. Here a systematic dynamical system analysis is developed for anisotropic Bianchi I cosmology with a massive disformally coupled vector field. Several new fixed points are found, including anisotropic scaling solutions. The formalism here presented can be conveniently applied to general scenarios with or without extra dimensional motivations. This is illustrated here by performing a complete analysis with the assumption that both the potentials and the warp factor for the brane are (nearly) exponential. In that case, the anisotropic fixed points are either not attractors, do not describe accelerating expansion or else they feature too large anisotropies to be compatible with observations. Nonetheless, viable classes of models exist where isotropy is retained due to rapid oscillations of the vector field, thus providing a possible realisation of disformally interacting massive dark matter.