Related papers: Stable non-BPS states in string theory: a pedagogi…
As of today there exist consistent, gauge-invariant string field theories describing all string theories: bosonic open and closed strings, open superstrings, heterotic strings and type II strings. The construction of these theories require…
We analyse the spectrum of non-BPS branes in the type I theory on the orbifold $T^4/{\cal I}_4$. We present a detailed analysis of the action of the worldsheet parity $\Omega$ on the different D-brane boundary state sectors of type IIB on…
Starting from the action of two coincident non-BPS D9-branes, we investigate kink configurations of the U(2) matrix tachyon field. We consider both Str and Tr prescriptions for the trace over gauge indices of the non-BPS action. Non-abelian…
We analyze the process of string vacuum destabilization due to instanton induced superpotential couplings which depend linearly on charged fields. These non-perturbative instabilities result in potentials for the D-brane moduli and lead to…
Type II strings in D=5 contain particle-like 1/8 supersymmetric BPS states. In this note we give a string-network representation of such states by considering (periodic) non-planar $(p,q,r)$-string networks of eight dimensional type II…
The purpose of this talk is to review a few issues concerning noncommutativity arising from String Theory. In particular, it is shown how in Type IIB Theory, the annihilation of a D3-\bar{D3} brane pair yields a D1-string. This object, in…
We discuss the open string one-loop partition function in tachyon condensation background of a unstable D-brane system. We evaluate the partition function by using the boundary state formulation and find that it is in complete agreement…
We study the infra-red limit of the O(N) gauge theory that describes the low energy modes of a system of $N$ type I D-strings and provide some support to the conjecture that, in this limit, the theory flows to an orbifold conformal theory.…
We show that the recent world-sheet analysis of the quantum fluctuations of a short flux tube in type II string theory leads to a simple and precise description of a pair of stuck D0branes in an orientifold compactification of the type I'…
We show that unstable D-branes play the role of ``D-sphalerons'' in string theory. Their existence implies that the configuration space of Type II string theory has a complicated homotopy structure, similar to that of an infinite…
We find exact tachyon kink solutions of DBI type effective action describing an unstable D5-brane with worldvolume gauge field turned on in a curved background. The background of interest is the ten-dimensional lift of the Salam-Sezgin…
We discuss the recent proposal that BPS D-branes in Calabi-Yau compactification of type II string theory are Pi-stable objects in the derived category of coherent sheaves.
We consider solitonic solutions of the DBI tachyon effective action for a non-BPS brane. When wrapped on a circle, these solutions are regular and have a finite energy. We show that in the decompactified limit, these solitons give Sen's…
We show that the strength of the leading non-perturbative effects in non-critical string theory is of the order $e^{-O(1/{\beta_{st}})}$. We show how this restricts the space of consistent theories. We also identify non-critical one…
In this note we reexamine the possibility of constructing stable non-supersymmetric theories that exhibit an exponential density of states. For weakly coupled closed strings there is a general theorem, according to which stable theories…
We use the `branes within branes' approach to study the appearance of stable $ (p-2)-branes and unstable (p-1)-branes in type II string theory from p-brane--p-antibrane pairs.Our goal is to describe the emergence of these lower dimensional…
We show that the $c=1$ bosonic string theory at finite temperature has two matrix-model realizations related by a kind of duality transformation. The first realization is the standard one given by the compactified matrix quantum mechanics…
The tachyonic instability of the open bosonic string is analyzed using the level truncation approach to string field theory. We have calculated all terms in the cubic action of the string field theory describing zero-momentum interactions…
In this paper we incorporate gauge fields into the tachyon field theory models for unstable D-branes in bosonic and in Type II string theories. The chosen couplings yield massless gauge fields and an infinite set of equally spaced massive…
We construct BRST invariant solitonic states in the OSp invariant string field theory for closed bosonic strings. Our construction is a generalization of the one given in the noncritical case. These states are made by using the boundary…