Rahul Nigam

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We study general two-body decays of primitive and non-primitive 1 4-BPS dyons in four-dimensional type IIB string compactifications. We find a " master equation " for marginal stability that generalises the curve found by Sen for 1 2-BPS decay, and analyse this equation in a variety of cases including decays to 1 4-BPS products. For 1 2-BPS decays, an(More)
We obtain the complete set of constraints on the moduli of N = 4 su-perstring compactifications that permit " rare " marginal decays of 1 4-BPS dyons to take place. The constraints are analysed in some special cases. The analysis extends in a straightforward way to multi-particle decays. We discuss the possible relation between general multi-particle decays(More)
We examine the duality between type 0 noncritical strings and topological B-model strings, with special emphasis on the flux dependence. The former theory is known to exhibit holomorphic factorisation upto a subtle flux-dependent disc term. We give a precise definition of the B-model dual and propose that it includes both compact and noncompact B-branes.(More)
I dedicate this thesis to my parents. Acknowledgements It is a pleasure to thank the many people who made this thesis possible. It is difficult to overstate my gratitude to my Ph.D. supervisor, Sandip Trivedi. With his enthusiasm, his inspiration, and his great efforts to explain things clearly and simply, he helped to make physics fun for me. Throughout my(More)
Declaration I state that the work, embodied in this thesis, forms my own contribution to the research work carried out under the guidance of Professor Sunil Mukhi. I also collaborated with Anindya Mukherjee while he was a student at TIFR. This work has not been submitted for any other degree to this or any other University or body. Whenever references have(More)
Assessing the nature and extent of damage due to natural calamities remains one of the thrust areas in monitoring resource inventory through remote sensing. The effect of the cyclone Phailin and the post-incessant rains during second fortnight of October 2013 on coastal Odisha was studied in terms of rice area flooded, submerged and damaged. Multi-temporal(More)
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