Alladi Ramakrishnan Hall

Rotating black holes as power sources

Pankaj Sheoran

Jamia Milia Islamia, New Delhi

In 1971 Roger Penrose pointed out that it was possible to extract the
the rotational energy of the Kerr black hole (BH), when a massive
particle enters into the ergosphere and splits up there into two. The
momentum of the two particles can be arranged in such a manner that
one piece escapes to infinity with energy greater than that of
incoming particle, while the other falls inside the event horizon of
the black hole. But through this process, we can extract at maximum
only 20% of energy of BH. Here, we investigate the properties of the
horizons and ergosphere in a rotating higher dimensional (HD) deformed
Kerr-like BH. Furthermore, we explicitly bring out the effect of
deformation parameter (ε) and the extra dimension (D) on the
efficiency of the Penrose process. It is interesting to see that the
ergosphere size is sensitive to the (ε) as well as spacetime
dimensions D. This gives rise to a much richer structure of the
ergosphere in a HD deformed Kerr BH, thereby making the Penrose
process more efficient compared with that of the four-dimensional Kerr
black hole.

We have also studied the Banados, Silk and West (BSW) effect for
rotating regular Ayón-Beato- García (ABG) BH in which two massive
particles moving in the equatorial plane collide near the event
horizon of a BH and the energy of their center-of-mass (CM) can grow
unbounded under certain conditions. It turns out that CM energy
depends not only on rotation parameter (a) as suggested by BSW but
also on charge (Q). Particularly for the extremal rotating regular ABG
BH, the CM energy of two colliding particles could be arbitrarily high
for the critical angular momentum of particles. Also, we have shown
that, for a nonextremal BH, there exists a finite upper limit of CM
energy, which changes with Q. Finally, we made a comparison with Kerr
and Kerr- Newman BHs.