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What is the relation between the entropy of rotating and non rotating Black hole?
Which one's entropy is greater?

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1 Answer 1

The entropy of a black hole is given by the area $A$ of its event horizon according to the formula $S=\frac{kA}{4l_P}$ where $k$ is Boltzmann's constant and $l_P$ is the Planck length.

For a rotating black hole with mass $M$ and a Kerr parameter $a$ the area is $A=\frac{8\pi G^2}{c^4}M(M+\sqrt{M^2-a^2})$. This is largest when $a=0$ corresponding to the non-rotating case. so the rotating black hole has less entropy than a static black hole of the same mass.

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