Biennial Report 2005-2007 - Saha Institute of Nuclear Physics

4 Biennial Report 2005-071.2.1.6 Quasinormal Modes of Stringy Black HolesIn this work we are studying the quasinormal modes (qnm) of stringy black holes. We are analyzingthe ADS/CFT correspondence for these extremal black holes using the qnm’s. We are alsoinvestigating the nature of the area law for the corresponding black hole entropy. This project hasbeen initiated in 2004 and is a part of the thesis work of Mr. Sayan Chakrabarti. One part of theproject has been completed where the relation between Scwarzschild geometry and the area lawquantization as proposed by Bekenstein has been clarified.Kumar S Gupta, Sayan ChakrabartiTheo1.2.1.7 Black Holes, Holography and Moduli Space MetricString theory can accommodate black holes with the black hole parameters related to string moduli.It is a well known but remarkable feature that the near horizon geometry of a large class of blackholes arising from string theory contains a BTZ part. A mathematical theorem (Sullivan’s Theorem)relates the three dimensional geometry of the BTZ metric to the conformal structures of a twodimensional space, thus providing a precise kinematic statement of holography. Using this theoremwe have shown that the string moduli space in this region has to have negative curvature from theBTZ part of the associated spacetime. This is consistent with a recent conjecture of Ooguri andVafa on string moduli space. This work was initiated and completed in 2006.Kumar S Gupta, S Sen†Theo1.2.1.8 Fundamental strings and NS5-branes from unstable D-branes in supergravityBy using the non-supersymmetric p-brane solutions delocalized in arbitrary number of transversedirections in type II supergravities, we show how they can be regarded as interpolating solutionsbetween unstable Dp-branes (a non-BPS D-brane or a pair of coincident D-brane-antiD-brane) andfundamental strings and also between unstable Dp-branes and NS5-branes. We also show that someof these solutions can be regarded as interpolating solutions between NS5/ NS5 ¯ and Dp-branes (forp ≤ 5). This gives a closed string description of the tachyon condensation and lends support to theconjecture that the open string theory on unstable D-branes at the tachyonic vacuum has solitonsolutions describing not only the lower dimensional BPS D-branes, but also the fundamental stringsas well as the NS5-branes.Jian-Xin Lu†, Shibaji RoyTheo1.2.1.9 Tachyon condensation on the intersecting brane-antibrane systemWe here generalize our study of the tachyon condensation on the brane-antibrane system to theintersecting brane-antibrane system. The supergravity solutions of the intersecting brane-antibranesystem are characterized by five parameters. We relate these parameters to the microscopic physicalparameters, namely, the number of Dp-branes (N 1 ), the number of ¯Dp-branes ( ¯N 1 ), the number of