We derive the complete (curvature) 2 terms of effective D-brane actions, for arbitrary ambient geometries and world-volume embeddings, at lowest order (disk-level) in the string-loop expansion. These terms reproduce the o(α ′ 2 ) corrections to string scattering amplitudes, and are consistent with duality conjectures. In the particular case of the D3brane with trivial normal bundle, considerations of SL(2, Z Z) invariance lead to a complete sum of D-instanton corrections for both the parity-conserving and the parity-violating parts of the effective action. These corrections are required for the cancellation of the modular anomalies of massless modes, and are consistent with the absence of chiral anomalies in the intersection domain of pairs of D-branes. We also show that the parity-conserving part of the non-perturbative R 2 action follows from a one-loop quantum calculation in the six-dimensional world-volume of the M5-brane compactified on a two-torus. 2/991

We derive boundary conditions for the covariant open string corresponding to D-branes in an Hpp-wave by requiring kappa-symmetry of its bulk action. Both half-supersymmetric and quarter-supersymmetric branes are seen to arise in this way, and the analysis furthermore agrees fully with the existing probe brane and supergravity computations. We elaborate on the origin of dynamical and kinematical supersymmetries from the covariant point of view. In particular we focus on the D-string which only preserves half of the dynamical supersymmetries and none of the kinematical ones. We discuss its origin in AdS 5 ϫS 5 and its world-volume spectrum.

We derive two families of supergravity solutions describing D-branes in the maximally supersymmetric Hpp-wave background. The first family of solutions corresponds to quarter-BPS D-branes. These solutions are delocalised along certain directions transverse to the pp-wave. The second family corresponds to the nonsupersymmetric D-branes. These solutions are fully localised. A peculiar feature of the nonsupersymmetric solutions is that gravity becomes repulsive close to the core of the D-brane. Both families preserve the amount of supersymmetry predicted by the D-brane probe/CFT analysis. All solutions are written in Brinkman coordinates. To construct these kind of solutions it is crucial to identify the coordinates in which the ansatz looks the simplest. We argue that the natural coordinates to get the supergravity description of the half-BPS branes are the Rosen coordinates.

Abstract:We study various aspects of the Kähler metric for matter fields in N = 1, 2 orientifold compactifications of type IIB string theory. The result has an infrared-divergent part which reproduces the field-theoretical anomalous dimensions, and a moduli-dependent part which comes from N = 2 sectors of the orientifold. For the N = 2 orientifolds, we also compute the disk amplitude for two matter fields on the boundary and a twisted closed string modulus in the bulk. Our results are in agreement with supersymmetry: the singlet under the SU(2) R R-symmetry has vanishing coupling, while the coupling of the SU(2) R triplet does not vanish.

We discuss some aspects of the generalization of the Born-Infeld action to non-abelian gauge groups and show how the discrepancy between Tseytlin's symmetrized trace proposal and string theory can be corrected at order F 6 . We also comment on the possible quadratic order fermionic terms.While the talk I gave at the Gong Show session of Cargèse' 99 Summer School was devoted to an outline of the main results of the paper "Curvature terms in D-brane actions and their M-theory origin" [1], this note will be focused on another very interesting but not yet settled aspect of the D-brane effective action : the generalization of the Dirac-Born-Infeld (DBI) action to non-abelian gauge groups.The massless degrees of freedom of an isolated D-brane are its transverse coordinates, a world-volume U (1) gauge field, and the associated fermions [2]. Its effective action contains a Dirac-Born-Infeld (DBI) (see [3] for a recent review of the DBI action) and a Wess-Zumino (WZ) piece. While the WZ part, describing the interactions of the D-brane with Ramond-Ramond field backgrounds, can be determined by anomaly cancellation and is therefore believed to be exact, the DBI piece is only reliable for small space-time curvatures, and in the low-acceleration regime. Indeed, for non constant gauge field strength, the DBI action is corrected by derivative terms [3,4].When N identical D-branes coincide, the transverse coordinates and world-volume gauge fields become N × N unitary matrices. The nonabelian generalization of the DBI action describing this dynamics has * LPTENS-99/34