It is conjectured that a rotating black hole has at its center a ring-shaped singularity.

Thus, at the center of the ring-shaped singularity the gravitational field must be zero (similar to gravitational field at center of dense object), and gravity must be minimized along the rotational axis. At the rotational axis, the gravitional field will be oriented towards the center from both sides, which will cause matter and eventually spacetime to flow towards the center.

Therefore, it seems plausible that the event horizon is a flattened ellipsoid that has upper and lower inward bulges that are rotationally symmetric around the rotational axis.

Also, for a very large black hole, the event horizon might open up around the rotational axis, such that the event horizon becomes toroidal (donut-shaped). Is that possible?

  • 2
    $\begingroup$ Please break this up into multiple questions. $\endgroup$ Apr 8, 2016 at 22:17
  • 1
    $\begingroup$ I think its best to keep as one question at least initially. Note that questions are simple derivations that provide context from the underlying question of whether matter can pass through the center of a ring-shaped singularity along the rotational axis, where the gravitational field points towards the center. $\endgroup$ Apr 8, 2016 at 22:54
  • 1
    $\begingroup$ No, the answers to these things are all radically different and have nothing to do with each other. $\endgroup$ Apr 8, 2016 at 23:05
  • 1
    $\begingroup$ It isn't 'conjectured': there is an exact solution whose properties have been extensively investigated. $\endgroup$
    – user107153
    Apr 9, 2016 at 8:34
  • 2
    $\begingroup$ Can someone reopen? $\endgroup$ Apr 9, 2016 at 18:07