Related papers: Stable non-BPS states in string theory: a pedagogi…
In these lecture notes duality tests and instanton effects in supersymmetric vacua of string theory are discussed. A broad overview of BPS-saturated terms in the effective actions is first given. Their role in testing the consistency of…
We construct two new SL(2,Z) invariant vacua of type IIB string theory which are bound states of $(p,q)$ strings with $(m,n)$ 5-branes, written as ((F, D1), (NS5, D5)) and preserve 1/4 of the full space-time supersymmetries. For the first…
We discuss the problem of tachyon condensation in the framework of background independent open string field theory. We show, in particular, that the computation of the string field theory action simplifies considerably if one looks at…
We have studied a problem of the tachyon mediated D-brane - D-brane annihilation from the underlying world-volume gauge field theory point of view. The initial state was chosen in the form of two D-branes crossing at a non-zero angle, which…
We search for tubular solutions in unstable D3-brane. With critical electric field E=1, solutions representing supertubes, which are supersymmetric bound states of fundamental strings, D0-branes, and a cylindrical D2-brane, are found and…
We investigate the D0-D4-brane system for different B-field backgrounds including the small instanton singularity in noncommutative SYM theory. We discuss the excitation spectrum of the unstable state as well as for the BPS D0-D4 bound…
We give a topological classification of stable and unconfined massive particles and strings (and some instantons) in worldvolume theories of M5-branes and their dimensional reductions, generalizing Witten's classification of strings in SYM.…
The study of open string tachyon condensation in string field theory can be drastically simplified by making an appropriate choice of coordinates on the space of string fields. We show that a very natural coordinate system is suggested by…
We consider tachyon condensation in unstable ten-dimensional heterotic string theory with gauge group E8. In the background of a lightlike linear dilaton rolling to weak coupling, we find an exact solution in which the theory decays to a…
The Dirac-Born-Infeld action with transverse scalar fields is considered to study the dynamics of various BPS states. We first describe the characteristic properties of the so-called 1/2 and 1/4 BPS states on the D3 brane, which can be…
F-theory on K3 admits non-BPS states that are represented as string junctions extending between 7-branes. We classify the non-BPS states which are guaranteed to be stable on account of charge conservation and the existence of a region of…
We investigate closed string tachyon condensation in Misner space, a toy model for big bang universe. In Misner space, we are able to condense tachyonic modes of closed strings in the twisted sectors, which is supposed to remove the big…
The moduli space of spiked instantons that arises in the context of the BPS/CFT correspondence is realised as the moduli space of classical vacua, i.e. low-energy open string field configurations, of a certain stack of intersecting…
Using string field theory, we argue that the tachyon potential on a D-brane anti-D-brane system in type II string theory in arbitrary background has a universal form, independent of the boundary conformal field theory describing the brane.…
We discuss how to describe time-dependent phenomena in string theory like the decay of unstable D-branes with the help of the world-sheet formulation. It is shown in a nontrivial well-controlled example that the coupling of the tachyons to…
It has been conjectured that at the stationary point of the tachyon potential for the D-brane-anti-D-brane pair or for the non-BPS D-brane of superstring theories, the negative energy density cancels the brane tensions. We study this…
The non-abelian flat directions in the tachyon potential of stable non-BPS branes recently found are shown to persist to all orders in alpha' at tree level in the string coupling. We also obtain the non-abelian Born-Infeld action including…
We study the open string pair production via the interaction of two parallel D$p$-branes. The branes have been dressed by the Kalb-Ramond field, a specific $U(1)$ gauge potential and a tachyon field of the open string spectrum. We shall…
We construct solitonic states in the OSp invariant string field theory, which are BRST invariant in the leading order of regularization parameter. One can show that these solitonic states describe D-branes and ghost D-branes, by calculating…
These lectures provide an introduction to the subject of tachyon condensation in the open bosonic string. The problem of tachyon condensation is first described in the context of the low-energy Yang-Mills description of a system of multiple…