Title: Quantum Tunnelling in Black Holes Authors: Bibhas Ranjan Majhi

This thesis is focussed towards the applications of the quantum tunnelling mechanism to study black holes. Here we give a general frame work of the existing tunnelling mechanism, both the radial null geodesic and Hamilton Jacobi methods. On the radial null geodesic method side, we study the modifications to the tunnelling rate, Hawking temperature and the Bekenstein- Hawking area law by including the back reaction as well as non-commutative effects in the space-time. A reformulation of the Hamilton-Jacobi (HJ) method is first introduced. Based on this, a close connection between the quantum tunnelling and the gravitational anomaly mechanisms to discuss Hawking effect, is put forwarded. An interesting advantage of this reformulated HJ method is that one can get directly the emission spectrum from the event horizon of the black hole, which was missing in the earlier literature. Also, the quantisation of the entropy and area of a black hole is discussed in this method. Another part of the thesis is the introduction of a new type of global embedding of curved space-time to higher dimensional Minkowskian space-time (GEMS). Using this a unified description of the Hawking and Unruh effects is given. Advantage of this approach is, it simplifies as well as generalises the conventional embedding. In addition to the spherically symmetric space-times, the Kerr-Newman black hole is exemplified. Finally, following the above ideas and the definition of partition function for gravity, it is shown that extremisation of entropy leads to the Einstein's equations of motion. In this frame work, a relation between the entropy, energy and the temperature of a black hole is given where energy is shown to be the Komar expression. Interestingly, this relation is the generalised Smarr formula. In this analysis, the GEMS method provides the law of equipartition of energy as an intermediate step.

Evidence of Macroscopic Quantum Tunnelling Detected in Nanowires A team of researchers at the University of Illinois has demonstrated that, counter to classical Newtonian mechanics, an entire collection of superconducting electrons in an ultrathin superconducting wire is able to "tunnel" as a pack from a state with a higher electrical current to one with a notably lower current, providing more evidence of the phenomenon of macroscopic quantum tunnelling. Physics professors Alexey Bezryadin and Paul Goldbart led the team, with graduate student Mitrabhanu Sahu performing the bulk of the measurements. Their research was published on the Web site of the journal Nature Physics on May 17.