Related papers: D-instanton and polyinstanton effects from type I'…
We evaluate string one-loop contributions to the Kahler metric of D-brane moduli (positions and Wilson lines), in toroidal orientifolds with branes at angles. Contributions due to bulk states in the loop are known, so we focus on the…
In this contribution we describe how to obtain instanton effects in four dimensional gauge theories by computing string scattering amplitudes in D3/D(-1) brane systems. In particular we show that the disks with mixed boundary conditions,…
The non-perturbative dynamics of quantum field theories is studied using theoretical tools inspired by string formalism. Two main lines are developed: the analysis of stringy instantons in a class of four-dimensional N=2 gauge theories and…
We study in detail the system of D6 branes and euclidean D2-brane instantons intersecting at angles in type IIA string theory. We find that in the absence of orientifolds the system does not contribute to the low energy superpotential, in…
We calculate instanton corrections to three dimensional gauge theories with N=4 and N=8 supersymmetry and SU(n) gauge groups. The N=4 results give new information about the moduli space of n BPS SU(2) monopoles, including the leading order…
In this paper we study the N=1 supersymmetric field theories realized on the world-volume of type IIB D3-branes sitting at orientifolds of non-orbifold singularities (conifold and generalizations). Several chiral models belong to this…
The R^4 terms in the effective action for M-theory compactified on a two-torus are motivated by combining one-loop results in type II superstring theories with the Sl(2,Z) duality symmetry. The conjectured expression reproduces precisely…
We identify and evaluate a class of physical amplitudes in four-dimensional N=4 superstring theory, which receive, in the weak coupling limit, contributions of order e^{-1/\lambda}, where \lambda is the type II superstring coupling…
We consider aspects of instanton dynamics in the large-N limit using the AdS/CFT duality for D0/D4 bound states. In the supergravity picture of wrapped D0-brane world-lines on D4-branes, we find the single-instanton measure and discuss its…
We examine the issue of generating the perturbatively absent ${\bf 10} \cdot {\bf 10} \cdot {{\bf 5}}^H$ SU(5)/flipped SU(5)Yukawa couplings in type II D-brane orientifold compactifications of string theory both at the perturbative (PER)…
We give a direct microscopic derivation of the F-theory background that corresponds to four D7 branes of type I' theory by taking into account the D-instanton contributions to the emission of the axio-dilaton field in the directions…
After orientifold projection, the conifold singularity in hypermultiplet moduli space of Calabi-Yau compactifications cannot be avoided by geometric deformations. We study the non-perturbative fate of this singularity in a local model…
A surprising relation between 4d $\mathcal{N}=2$ class $\mathcal{S}$ superconformal field theories of Type-$A$ and 6d $\mathcal{N}=(1,0)$ orbi-instanton theories is investigated. We find that all of the theories in the former class can be…
We extend the study of superinstantons presented in 1905.01513 to include orthosymplectic supergroup gauge theories, $B_{n_0|n_1}$, $C_n$, and $D_{n_0|n_1}$. We utilize equivariant localization to obtain the LMNS contour integral formula…
We investigate boundary dynamics of orbifold conformal field theory involving T-duality twists. Such models typically appear in contexts of non-geometric string compactifications that are called monodrofolds or T-folds in recent literature.…
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…
We study the embedding of D(8-p)-branes in the background geometry of parallel Dp-branes for $p\le 6$. The D(8-p)-brane is extended along the directions orthogonal to the Dp-branes of the background. The D(8-p)-brane configuration is…
We study the combined effect of world-volume and background fluxes on Euclidean D3-brane instantons in F-theory compactifications. We derive an appropriate form of the fermionic effective action, in which the fermions are topologically…
We study D-instanton solutions in type IIB supergravity on $AdS_5\times T^{1,1}$, which has a dual ${\cal N}=1$ $SU(N)\times SU(N)$ super Yang-Mills theory. Apart from ordinary D(-1)-brane instantons, we discuss wrapped D1-branes over…
A D-instanton is a space-time event associated with world-sheet boundaries that contributes non-perturbative effects of order $e^{-const/\kappa}$ to closed-string amplitudes. Some properties of a gas of D-instantons are discussed in this…