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This is an introduction to the properties of D-branes, topological defects in string theory on which string endpoints can live. D-branes provide a simple description of various nonperturbative objects required by string duality, and give…

Non-extremal intersecting p-brane solutions of gravity coupled with several antisymmetric fields and dilatons in various space-time dimensions are constructed. The construction uses the same algebraic method of finding solutions as in the…

We consider two Dirichlet p-branes with lower dimensional brane charges and their scattering. We first calculate the cylinder amplitude of open string with suitable boundary conditions. We compare this result with that in the IIB matrix…

Fluxbrane-like backgrounds obtained from flat space by a sequence of T-dualities and shifts of polar coordinates (beta deformations) provide an interesting class of exactly solvable string theories. We compute the one-loop partition…

Techniques of non-commutative field theories have proven to be useful in describing D-branes as tachyonic solitons in open string theory. However, this procedure also leads to unwanted degeneracy of solutions not present in the spectrum of…

Recently, it has been observed that the IIB scattering amplitudes are compatible with the standard rules of S-duality. Inspired by this observation, we will find the tree-level S-matrix elements of one Ramond-Ramond and three open strings…

A manifestly S-dual, and `12 dimensional', IIB superstring action with an $Sl(2;\bR)$ doublet of `Born-Infeld' fields is presented. The M-theory origin of the 12th dimension is the M-2-brane tension, which can be regarded as the flux of a…

We study the existence of D-brane bound states at threshold in Type II string theories. In a number of situations, we can reduce the question of existence to quadrature, and the study of a particular limit of the propagator for the system…

T-duality realized on D-brane effective actions is studied from a pure worldvolume point of view. It is proved that invariance in the form of the Dirac-Born-Infeld and Wess-Zumino terms fixes the T-duality transformations of the NS-NS and…

We discuss general spinning p-branes of string and M-theory and use their thermodynamics along with the correspondence between near-horizon brane solutions and field theories with 16 supercharges to describe the thermodynamic behavior of…

In assumption,that string model is the integrable model for particular kind of the background fields, the closed string model in the background gravity field and the antisymmetric B-field is considered as the bihamiltonian system. It is…

This is an introduction to two-dimensional conformal field theory and its applications in string theory. Modern concepts of conformal field theory are explained, and it is outlined how they are used in recent studies of D-branes in the…

When an NS5-brane crosses a D6-brane, a D4-brane is created stretching between them by the Hanany-Witten effect. However, the T-dual situation involves a Kaluza-Klein monopole crossing a D5-brane and should not result in brane creation.…

Unstable D-branes are central objects in string theory, and exist also in time-dependent backgrounds. In this paper we take first steps to studying brane decay in spacetime orbifolds. As a concrete model we focus on the R^{1,d}/Z_2…

In the presence of background Neveu-Schwarz flux, the description of the Ramond-Ramond fields of type IIB string theory using twisted K-theory is not compatible with S-duality. We argue that other possible variants of twisted K-theory would…

We use rotation of one D-brane with respect to the other to reveal the hidden structure of D-branes in type-II theories. This is done by calculation of the interaction amplitude for two different parallel and angled branes. The analysis of…

The aim of these notes is to give recent developments in string theory. In particular, we discuss the string spectrums, compactifications, brane physics and dualities.

We propose a method for constructing super-brane actions where every background tensor potential corresponds to a world-volume field strength. The procedure provides a natural coupling to the background and automatically displays the…

We describe a simple method for generating new string solutions for which the brane worldvolume is a curved space. As a starting point we use solutions with NS-NS charges combined with 2-d CFT's representing different parts of space-time.…

We review the recent developments in our understanding of non-BPS states and branes in string theory. The topics include 1) construction of unstable non-BPS D-branes in type IIA and type IIB string theories, 2) construction of stable…