Related papers: Unoriented D-brane Instantons vs Heterotic worldsh…
We review some aspects of D-instantons in intersecting D-brane models. In particular, we present applications of the recently proposed instanton calculus to computations of charged matter superpotential couplings and corrections to the…
We define fermionic collective coordinates for type-IIB Dirichlet instantons and discuss some effects of the associated fermionic zero modes within the dilute gas framework. We show that the standard rules for clustering of zero modes in…
Type IIA orientifold constructions with intersecting D6-branes and their IIB duals in terms of magnetized D9/D7-branes constitute one of the most promising avenues for the construction of semirealistic MSSM-like compactifications. One…
We consider string pair production in non homogeneous electric backgrounds. We study several particular configurations which can be addressed with the Euclidean world-sheet instanton technique, the analogue of the world-line instanton for…
Two dimensional N=(4,4) gauge theories flow to interacting superconformal field theories on their Higgs branch. We examine worldsheet instantons in these theories through the eyes of a D-brane construction. The effective instanton partition…
We present new SO(4)-invariant and non-supersymmetric instanton solutions for the conformally coupled m^2=-2 and massive m^2=+4 (pseudo)scalars arising from a consistent truncation of 11-dimensional supergravity over AdS_4 x S^7/Z_k when…
Quantum non-perturbative geometry of the universal hypermultiplet is investigated. We consider the simple case when the D-instantons, originating from the Calabi-Yau wrapped D2-branes, preserve a U(1)xU(1) symmetry of the universal…
The Yukawa couplings of the simpler models of D-branes on toroidal orientifolds suffer from the so-called ``rank one'' problem -- there is only a single non-zero mass and no mixing. We consider the one-loop contribution of E2-instantons to…
We study two-dimensional SQED viewed as the world-volume theory of a D-string in the presence of D5-branes with non-zero background fields that induce attractive forces between the branes. In various approximations, the low-energy dynamics…
We compute the gravitational coupling $F_1$ for IIA string theory on $K3 \times T^2$ and use string-string duality to deduce the corresponding term for heterotic string on $T^6$. The latter is an infinite sum of gravitational instanton…
According to the covariant open superstring description of 1/2-BPS D-branes in the AdS$_5\times$S$^5$ background, there are two kinds of purely instantonic D-branes. One is the well known D(-1)-brane or D-instanton, and another is the…
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…
We study the non-commutative instanton solution proposed in hep-th/0009142 and obtain the spectrum of small oscillations. The spectrum thus obtained is in exact agreement with the spectrum of stringy excitations in a configuration of point…
We study different aspects of the non-perturbative superpotentials induced by Euclidean E3-branes on systems of D3/D7-branes located at Abelian orbifold singularities. We discuss in detail how the induced couplings are consistent with the…
This introductory part of the author's PhD compilation thesis discusses non-perturbative aspects of string theory, with focus on D-instantons which play key roles in the context of string phenomenology and dualities. By translating ideas…
Non-perturbative D-brane instanton effects in 4d N = 1 string compactifications can be geometrized in terms of a backreacted generalized geometry. We extend earlier results to setups in which the D-brane instanton is charged under the 4d…
Thus far, there seem to be no complete criteria that can settle the issue as to what the correct generalization of the Dirac-Born-Infeld (DBI) action, describing the low-energy dynamics of the D-branes, to the non-abelian case would be.…
Using instanton effects, we discuss the problem of fermion mass hierarchies in an MSSM-like Type IIA orientifolded model with U(3)xSp(1)xU(1)xU(1) gauge symmetry obtained from intersecting D6-branes. In the corresponding four-stack quiver,…
Similar to the Schwinger effect in the quantum electrodynamics, a system of two parallel D-branes at a finite separation can produce open string pairs through their interaction. In this paper, we investigate this rate for the dressed…
D-brane instantons can perturb the quantum field theories on space-time filling D-branes by interesting operators. In some cases, these D-brane instantons are novel "stringy" effects (not interpretable directly as instanton effects in the…