Boundary States of D-branes in AdS_3 Based on Discrete Series

We study D-branes in the Lorentzian AdS_3 background from the viewpoint of boundary states, emphasizing the role of open-closed duality in string theory. Employing the world sheet with Lorentzian signature, we construct the Cardy states with the discrete series. We show that they are compatible with (1) unitarity and normalizability, and (2) the spectral flow symmetry, in the open string spectrum. We also discuss their brane interpretation. We further show that in the case of superstrings on AdS_3 x S^3 x T^4, our Cardy states yield an infinite number of physical BPS states in the open string channel, on which the spectral flows act consistently.Comment: 27 pages, latex, no figures, v2: we discuss on the single cover of AdS_3 rather than the universal cover, reference added, v3: Appendix B and reference adde

Marginal deformations of 3d supersymmetric U(N) model and broken higher spin symmetry

We examine the marginal deformations of double-trace type in 3d supersymmetric U(N) model with N complex free bosons and fermions. We compute the anomalous dimensions of higher spin currents to the 1/N order but to all orders in the deformation parameters by mainly applying the conformal perturbation theory. The 3d field theory is supposed to be dual to 4d supersymmetric Vasiliev theory, and the marginal deformations are argued to correspond to modifying boundary conditions for bulk scalars and fermions. Thus the modification should break higher spin gauge symmetry and generate the masses of higher spin fields. We provide supports for the dual interpretation by relating bulk computation in terms of Witten diagrams to boundary one in conformal perturbation theory.Comment: 32 pages, 3 figures, minor changes, references added, published versio

Branes in the OSP(1|2) WZNW model

The boundary OSP(1|2) WZNW model possesses two types of branes, which are localized on supersymmetric Euclidean AdS$_2$ and on two-dimensional superspheres. We compute the coupling of closed strings to these branes with two different methods. The first one uses factorization constraints and the other one a correspondence to boundary N=1 super-Liouville field theory, which we proof with path integral techniques. We check that the results obey the Cardy condition and reproduce the semi-classical computations. For the check we also compute the spectral density of open strings that are attached to the non-compact branes.Comment: 60 page

Conformal blocks from Wilson lines with loop corrections

We compute the conformal blocks of the Virasoro minimal model or its W$_N$ extension with large central charge from Wilson line networks in a Chern-Simons theory including loop corrections. In our previous work, we offered a prescription to regularize divergences from loops attached to Wilson lines. In this paper, we generalize our method with the prescription by dealing with more general operators for $N=3$ and apply it to the identity W$_3$ block. We further compute general light-light blocks and heavy-light correlators for $N=2$ with the Wilson line method and compare the results with known ones obtained using a different prescription. We briefly discuss general W$_3$ blocks.Comment: 53 pages, 6 figures, v2: an appendix analyzing a general W$_3$ block added, v3: minor changes, published versio