# Velocity of ringularity

How fast is a ringularity1 spinning? Spinning black holes are created from spinning stars.

The angular momentum of the 'parent' star must be conserved so spinning black holes are spinning much much faster than their 'parent' star.

Since black holes have generally less mass than their parent star and mass is found only in a tiny amount of space then the ringularity should be spinning incredibly fast.

The ringularity is a ring which contains all the mass of the black hole and it is in the center and it is almost infinitely tiny so it must be spinning almost infinitely fast.

Can it spin faster than c? Is there any way to know if SR can be violated inside such extremely dense objects?

• If SR is special relativity, it is not a good approximation of the physics in the vicinity of a black hole because special relativity excludes the effects of gravity. – antispinwards Jul 14 at 17:37
• I don't say it is but could it possible it is violated near the ringularities? – Helena Wells Jul 14 at 17:47

$$K_\text{min}=2\pi\sqrt{a^2+3(ma^2)^{2/3}} \tag{1}$$

where the quantities $$m$$ and $$a$$, both of which have units of length, are defined by $$m=\frac{GM}{c^2} \hskip2cm a=\frac{J}{Mc}. \tag{2}$$

The maximum spin is a=m (an extremal Kerr black hole), the borderline case between a black hole and a naked singularity.

More details from Chiral Anomaly here: https://physics.stackexchange.com/a/469282/

• Ok i am not really a math guy can you tell me if the ringularity can be spinning faster than c? – Helena Wells Jul 14 at 4:39
• @Helena As Chiral Anomaly says, "The geometry inside a Kerr black hole is pretty crazy". In GR, you can apply SR in a sufficiently small region of spacetime, where "sufficiently small" means that the effects of curvature in that region are small enough to be negligible. But the effects of curvature are never negligible if the region contains a singularity. So trying to apply the geometric notions of SR to the ringularity itself doesn't work. – PM 2Ring Jul 14 at 10:27
• This isn't really a helpful answer. I don't see velocity mentioned and $K_{\rm min}$ is undefined. – Rob Jeffries Jul 14 at 13:29
• Velocity relative to what? – user253751 Jul 14 at 14:54
• @user253751 if special relativity breaks down near the ringularity then it could be anything. – Helena Wells Jul 14 at 17:52