发表机构
Savitribai Phule Pune University; Birla Institute of Technology and Science, Pilani, Hyderabad Campus（萨维特里拜·普莱·浦那大学; 比拉理工学院，海德拉巴校区）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究分析修正引力中三种旋转时空的闭合类时曲线，证明额外参数可解析控制并消除赤道面上的破坏因果性区域。
AI 中文摘要
我们研究了修正引力中出现的三个旋转时空中的闭合类时曲线（CTCs）：潮汐荷膜世界黑洞、Rastall引力中的Kerr-Newman黑洞以及带电的Johannsen-Psaltis时空。利用赤道面上$g_{\phi\phi}$的符号，我们表明每个几何的额外参数控制着破坏因果性区域，并解析地获得了临界参数值。在膜世界情形中，正的$r$ CTC区域仅存在于正潮汐荷时，且对于$q\leq 0$完全消失。在Rastall引力中，CTC区域的范围同时取决于Rastall耦合和周围物质。对于每种物质类型，我们找到了一个有限的耦合范围，在该范围内CTC区域不存在。在带电的Johannsen-Psaltis时空里，形变参数可以依据径向位置增加或减小$g_{\phi\phi}$，我们推导出其取值的一个窗口，在该窗口内CTC区域从所考虑的径向域中被移除。因此，在所有三个例子中，额外参数可以被选择来控制赤道CTCs的范围，甚至完全消除它们。
英文摘要
We study closed timelike curves (CTCs) in three rotating spacetimes arising in modified gravity: the tidally charged braneworld black hole, the Kerr-Newman black hole in Rastall gravity, and the charged Johannsen-Psaltis spacetime. Using the sign of $g_{ϕϕ}$ on the equatorial plane, we show that an additional parameter of each geometry controls the chronology-violating region, and we obtain critical parameter values analytically. In the braneworld case, the positive $r$ CTC region exists only for positive tidal charge and disappears completely for $q\leq 0$. In Rastall gravity, the extent of the CTC region depends jointly on the Rastall coupling and the surrounding matter. For each matter type we find a finite range of the coupling for which the CTC region is absent. In the charged Johannsen-Psaltis spacetime, the deformation parameter can either increase or decrease $g_{ϕϕ}$ depending on the radial position, and we derive a window of its values for which the CTC region is removed from the radial domain considered. Thus, in all three examples, the additional parameters can be chosen to control the extent of equatorial CTCs, and even to eliminate them entirely.
Comments18 pages, 6 Figures
