We study extremal black hole solutions in D dimensions with near horizon geometry AdS2 Ã— S in higher derivative gravity coupled to other scalar, vector and antisymmetric tensor fields. We define anâ€¦ (More)

The tachyon effective field theory describing the dynamics of a non-BPS D-brane in superstring theory has an infinitely thin but finite tension kink solution describing a codimension one BPS D-brane.â€¦ (More)

In this review we describe our current understanding of the properties of open string tachyons on an unstable D-brane or brane-antibrane system in string theory. The various string theoretic methodsâ€¦ (More)

The spectrum of quarter BPS dyons in N = 4 supersymmetric string theories can change as the asymptotic moduli cross walls of marginal stability on which the dyon can break apart into a pair of halfâ€¦ (More)

We discuss a general iterative procedure for constructing time dependent solutions in open string theory describing rolling of a generic tachyon field away from its maximum. These solutions areâ€¦ (More)

Recent investigations involving the decay of unstable D-branes in string theory suggest that the tree level open string theory which describes the dynamics of the D-brane already knows about theâ€¦ (More)

In these lecture notes we describe recent progress in our understanding of attractor mechanism and entropy of extremal black holes based on the entropy function formalism. We also describe preciseâ€¦ (More)

It has recently been shown that if we take into account a class of higher derivative corrections to the effective action of heterotic string theory, the entropy of the black hole solutionâ€¦ (More)

We review and extend recent attempts to find a precise relation between extremal black hole entropy and degeneracy of microstates using AdS 2 /CF T 1 correspondence. Our analysis leads to a specificâ€¦ (More)