Geodesic causality in Kerr spacetimes with $|a|\geq M$

Giulio Sanzeni; Karim Mosani

doi:10.1016/j.geomphys.2025.105589

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arXiv · 2504.17763

Geodesic causality in Kerr spacetimes with $|a|\geq M$

Giulio Sanzeni·Karim Mosani

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Abstract

The analytic extension of the Kerr spacetimes into the negative radial region contains closed causal curves for any non-zero rotation parameter $a$ and mass parameter $M$. Furthermore, the spacetimes become totally vicious when $|a|>M$, meaning that through every point there exists a closed timelike curve. Despite this, we prove that the Kerr spacetimes do not admit any closed null geodesics when $|a|\geq M$. This result generalises recent findings by one of the authors, which showed the nonexistence of closed causal geodesics in the case $|a|<M$. Combining these results, we establish the absence of closed null geodesics in Kerr spacetimes for any non-zero $a$.

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BibTeX RIS

Giulio Sanzeni, Karim Mosani. 2025-04-24. Geodesic causality in Kerr spacetimes with $|a|\geq M$. https://doi.org/10.1016/j.geomphys.2025.105589

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