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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…
We show that bosonic D-brane states may be represented as coherent states in an open string representation. By using the Thermo-Field Dynamics (TFD) formalism, we may construct a condensed state of open string modes which encodes the…
A class of D-branes for the type IIB plane-wave background is considered that preserve half the dynamical supersymmetries of the light-cone gauge. The D-branes of this type are the euclidean (or instantonic) (0,0), (0,4) and (4,0) branes…
Cosmic strings in realistic particle physics models have fermion zero modes in the string core. Such zero modes change the underlying cosmology; for example, the string can carry a current. We consider the stability of fermion zero modes to…
A new configuration of non-abelian D1-branes growing into D5-branes is found. This time the effect is triggered by a non-trivial electric field on the world-volume of the D1-branes and a constant RR 4-form potential. Based on the these…
We review for non-experts possible phenomenological scenari in String Theory. In particular we focus on vacuum configurations with intersecting and/or magnetized unoriented D-branes. We will show how a TeV scale tension may be compatible…
We consider a D-brane probe in unstable string background associated with flux branes. The twist in spacetime metric reponsible for the supersymmetry breaking is shown to manifest itself in mixing of open Wilson lines with the phases of…
Using E-strings, we can analyze not only six-dimensional superconformal field theories but also probe vacua of non-perturabative heterotic string. We study strings made of D3-branes wrapped on various two-cycles in the global F-theory…
We study the symmetry structure of N=8 quantum mechanics, and apply it to the physics of D0-brane probes in type I' string theory. We focus on the theory with a global $Spin(8)$ R symmetry which arises upon dimensional reduction from $2d$…
Proceeding from nonlinear realizations of (super)conformal symmetries, we explicitly demonstrate that adding the harmonic oscillator potential to the action of conformal mechanics does not break these symmetries but modifies the…
We address the bosonic string pair creation in a system of parallel Dp-Dp' (p<p') branes by applying the path integral formalism. We drive the string pair creation rate by calculating the one loop vacuum amplitude of the setup in presence…
In this article, we investigate zero-modes for a dynamical (rotating-moving) D$p$-brane, coupled to the electromagnetic and tachyonic background fields. This work is done by the boundary state methods, in three cases of bosonic and…
We construct new intersecting S-brane solutions in 11-dimensional supergravity which do not have supersymmetric analogs. They are obtained by letting brane charges to be proportional to each other. Solutions fall into two categories with…
We show that the one loop amplitudes of open and closed string theory in a constant background two-form tensor field are characterized by an effective string tension larger than the fundamental string tension, and by the appearance of…
We study the objects (called spectral branes or S-branes) which are obtained by imposing non-local spectral boundary conditions at the boundary of the world sheet of the bosonic string. They possess many nice properties which make them an…
We show how the Wess-Zumino terms of the different branes in string theory can be embedded within double field theory. Crucial ingredients in our construction are the identification of the correct brane charge tensors and the use of the…
The non-commutative geometry of a large auxiliary $B$-field simplifies the construction of D-branes as solitons in open string field theory. Similarly, fundamental strings are constructed as localized flux tubes in the string field theory.…
We present a string theory construction in which the particle physics contributions to the one-loop vacuum energy exactly cancel, whilst the gravitational contributions are suppressed in the size of one or two large extra dimensions. This…
The past year has seen enormous progress in string theory. It has become clear that all of the different string theories are different limits of a single theory. Moreover, in certain limits, one obtains a new, eleven-dimensional structure…
1. Preliminaries. 2. Heterotic string and motivations for large volume compactifications; 2.1 Gauge coupling unification; 2.2 Supersymmetry breaking by compactification. 3. M-theory on S^1/Z_2 \times Calabi-Yau. 4. Type I/I' string theory…