Related papers: Solution Generating Technique for Noncommutative O…

We present special classes of orientifold models involving supersymmetry breaking via branes at angles. Type II superstring theories are compactified on a two torus times a four-dimensional orbifold. Combining worldsheet parity with a…

The decay of rotated brane configurations and the corresponding condensation of tachyons is discussed. In a certain IIB orbifold case a heuristic argument about the mass of the state living on the fixed plane is made. When the rotation…

This paper is devoted to the construction of unstable D-brane action in torsional Newton-Cartan background through T-duality along null direction. We determine corresponding equations of motion and analyze their solution that corresponds to…

We study the process of inhomogeneous tachyon condensation in an intersecting D1- and anti-D1-brane system using an effective tachyon DBI action. By switching to the Hamiltonian formalism, we numerically solve for the dynamical evolution of…

We derive novel solutions of flux compactification with D7-branes on the resolved conifold in type IIB String Theory and later extend this solution to allow for non-zero temperature. At zero temperature, we find that adding D7-branes via…

We discuss tachyon-free examples of (Type IIB on) non-compact non-supersymmetric orbifolds. Tachyons are projected out by discrete torsion between orbifold twists, while supersymmetry is broken by a Scherk-Schwarz phase (+1/-1 when acting…

We study the spectrum of stable BPS and non-BPS D-branes in Z_2 x Z_2 orientifolds for all choices of discrete torsion between the orbifold and orientifold generators. We compute the torsion K-theory charges in these D=4, N=1 orientifold…

We consider an unstable bound system of two supersymmetric Dirichlet branes of different dimensionality ($p,p'$ with $p'<p$) embedded in a flat non-compactified IIA or IIB type background. We study the decay, via tachyonic condensation, of…

We investigate tachyon production in noncommutative de Sitter space by solving the deformed Klein-Gordon equation. Using the Bogoliubov transformation method, we compute the number density of created scalar tachyons and demonstrate that…

We study non-perturbative effects in four-dimensional N=1 supersymmetric orientifold compactifications due to D-brane instantons which are generically not invariant under the orientifold projection. We show that they can yield…

We construct D-branes in a left-right asymmetrically gauged WZW model, with the gauge subgroup embedded differently on the left and the right of the group element. The symmetry-preserving boundary conditions for the group-valued field $g$…

In this paper we will consider the dynamics of BPS and non-BPS Dp-branes in the background of N Dk-branes. Our approach is based on an existence of the new symmetry of D-brane effective actions that naturally emerges in the near horizon…

We investigate the string field theory around the tachyon vacuum. A pure gauge form of the solution is constructed at the tachyon vacuum. For a special choice of the gauge function for the pure gauge form, marginal deformation from the…

Using the type II near-extremal 3D-branes solution we apply the T-duality and smeared twist to construct the supergravity backgrounds which dual to the 4D finite temperature non-commutative dipole field theories. We first consider the…

We present a tachyon field, which simply connects to the calculus of the tachyon condensation. The tachyon field acts on any bare boundary state: the Neumann or the Dirichlet state, and generates the boundary state suggested by S.P. de…

Starting with the D-dimensional Einstein-dilaton-antisymmetric form equations and assuming a block-diagonal form of a metric we derive a $(D-d)$-dimensional $\sigma$-model with the target space $SL(d,R)/SO(d) \times SL(2,R)/SO(2) \times R$…

In this paper, we construct degenerate soliton solutions (which preserve $\cal{PT}$-symmetry/break $\cal{PT}$-symmetry) to the nonlocal Manakov system through a nonstandard bilinear procedure. Here by degenerate we mean the solitons that…

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…

We discuss the lift of certain D6-antiD6-brane systems to M-theory. These are purely gravitational configurations with a bolt singularity. When reduced along a trivial circle, and for large bolt radius, the bolt is related to a…

We begin by reviewing the results on the decay of unstable D-branes in type II string theory, and the open-closed string duality proposal that arises from these studies. We then apply this proposal to the study of tachyon driven cosmology,…