Related papers: D-branes, open string vertex operators, and Ext gr…

We discuss carefully the vertices which describe the dipole open strings and closed strings on a D-brane with magnetic flux on a torus. Translation invariance along closed cycles forces surprisingly closed string vertices written in open…

Polchinski's recent construction of Dirichlet-branes of R-R charges, together with Witten's mechanism for forming bound states of both NS-NS charges and R-R charges, provides a rigorous method to treat these dy-branes. We construct the…

In type-II string theory compactifications on Calabi-Yau manifolds, topological string theory partition functions give a class of exact F-terms in the four-dimensional effective action. We point out that in the background of constant…

D-branes on one-parameter Calabi-Yau spaces and two-parameter K3-fibered Calabi-Yau manifolds are analyzed from both the Gepner model point of view and the geometric perspective. We compute part of the spectrum of the boundary states and…

Boundary states for D-branes are constructed using the light cone gauge. The D-brane breaks half the spacetime supersymmetry giving rise to fermionic zero modes living on the brane. The nonlinear realization of the broken supersymmetry on…

We describe the general geometrical framework of brane world constructions in orientifolds of type IIA string theory with D6-branes wrapping 3-cycles in a Calabi-Yau 3-fold, and point out their immediate phenomenological relevance. These…

Witten couples the open topological B-model to a holomorphic vector bundle by adding to the boundary of the worldsheet a Wilson loop for an integrable connection on the bundle. Using the descent procedure for boundary vertex operators in…

We study pairs of planar D-branes intersecting on null hypersurfaces, and other related configurations. These are supersymmetric and have finite energy density. They provide open-string analogues of the parabolic orbifold and null-fluxbrane…

We discuss type IIB orientifolds with D-branes, and NSNS and RR field strength fluxes. The D-brane sectors lead to open string spectra with non-abelian gauge symmetry and charged chiral fermions. The closed string field strengths generate a…

Closed string dynamics in the presence of noncommutative Dp-branes is investigated. In particular, we compute bulk closed string two-point scattering amplitudes; the bulk space-time geometries encoded in the amplitudes are shown to be…

We analyze one loop scattering amplitudes of the massless states on a stack of D3-branes. We use the vertex operators that have been obtained in the direct open string analysis developed in arXiv:0708.3452. The method does not have the…

We study effective quiver gauge theories arising from a stack of D3-branes on certain Calabi-Yau singularities. Our point of view is a first principle approach via open topological string theory. This means that we construct the natural…

In this paper we construct complete macroscopic operators in two dimensional type 0 string theory. They represent D-branes localized in the time direction. We give another equivalent description of them as deformed Fermi surfaces. We also…

In this thesis we study string theory with D-branes and possibly orientifolds in curved or time-dependent spaces. Our study aims at understanding some aspects of curved and time-dependent spaces, notably because of their importance in…

The boundary chiral ring of a 2d gauged linear sigma model on a K\"ahler manifold $X$ classifies the topological D-brane sectors and the massless open strings between them. While it is determined at small volume by simple group theory, its…

We consider freely acting orbifold compactifications, which interpolate in two possible decompactification limits between the supersymmetric type II string and the non-supersymmetric type 0 string. In particular we discuss how D-branes are…

Brane-like states are defined by physical vertex operators in NSR superstring theory, existing at nonzero pictures only. These states exist both in open and closed string theories, in the NS and NS-NS sectors respectively. In this paper we…

In our continued efforts of matching full string computations with the corresponding effective field theory computations, we evaluate string theory correlators in closed forms. In particular, we consider a correlator between three SYM…

We construct D-brane states on an asymmetric orbifold of type IIA on a four-torus, which is modded out by T-duality. We find explicit boundary states charged under the twisted sector gauge fields. Unlike other cases, the boundary states…

We perform a Hodge theoretic study of parameter dependent families of D-branes on compact Calabi-Yau manifolds in type II and F-theory compactifcations. Starting from a geometric Gauss-Manin connection for B type branes we study the…