Superconformal defects in the tricritical Ising model

We study superconformal defect lines in the tricritical Ising model in 2 dimensions. By the folding trick, a superconformal defect is mapped to a superconformal boundary of the N=1 superconformal unitary minimal model of c=7/5 with D_6-E_6 modular invariant. It turns out that the complete set of the boundary states of c=7/5 D_6-E_6 model cannot be interpreted as the consistent set of superconformal defects in the tricritical Ising model since it does not contain the "no defect" boundary state. Instead, we find a set of 18 consistent superconformal defects including "no defect" and satisfying the Cardy condition. This set also includes some defects which are not purely transmissive or purely reflective.Comment: 25 pages, 3 figures. v2: typos corrected. v3: clarification about spin structure aligned theory added, references adde

D-branes in the WZW model

It is stated in the literature that D-branes in the WZW-model associated with the gluing condition J = - \bar{J} along the boundary correspond to branes filling out the whole group volume. We show instead that the end-points of open strings are rather bound to stay on `integer' conjugacy classes. In the case of SU(2) level k WZW model we obtain k-1 two dimensional Euclidean D-branes and two D particles sitting at the points e and -e.Comment: 2 pages, LaTe

On supersymmetric interfaces for string theory

We construct the world-sheet interface which preserves space-time supersymmetry in type II superstring theories in the Green-Schwarz formalism. This is an analog of the conformal interface in two-dimensional conformal field theory. We show that a class of the supersymmetric interfaces generates T-dualities of type II theories, and that these interfaces have a geometrical interpretation in the doubled target space. We compute the partition function with a pair of the supersymmetric interfaces inserted, from which we read off the spectrum of the modes coupled to the interfaces and the Casimir energy between them. We also derive the transformation rules under which a set of D-branes is transformed to another by the interface.Comment: 1+23 pages, 1 figure; (v2) added comments, made changes in presentatio

Orientifolds of type IIA strings on Calabi-Yau manifolds

We identify type IIA orientifolds that are dual to M-theory compactifications on manifolds with G_2-holonomy. We then discuss the construction of crosscap states in Gepner models. (Based on a talk presented by S.G. at PASCOS 2003 held at the Tata Institute of Fundamental Research, Mumbai during Jan. 3-8, 2003.)Comment: 3 pages, RevTeX, PASCOS '03 tal

Manifestly Supersymmetric RG Flows

Renormalisation group (RG) equations in two-dimensional N=1 supersymmetric field theories with boundary are studied. It is explained how a manifestly N=1 supersymmetric scheme can be chosen, and within this scheme the RG equations are determined to next-to-leading order. We also use these results to revisit the question of how brane obstructions and lines of marginal stability appear from a world-sheet perspective.Comment: 22 pages; references added, minor change

The Landau-Ginzburg to Calabi-Yau Dictionary for D-Branes

Based on work by Orlov, we give a precise recipe for mapping between B-type D-branes in a Landau-Ginzburg orbifold model (or Gepner model) and the corresponding large-radius Calabi-Yau manifold. The D-branes in Landau-Ginzburg theories correspond to matrix factorizations and the D-branes on the Calabi-Yau manifolds are objects in the derived category. We give several examples including branes on quotient singularities associated to weighted projective spaces. We are able to confirm several conjectures and statements in the literature.Comment: 24 pages, refs added + minor correctio

Gravitino condensation in fivebrane backgrounds

We calculate the tension of the D3-brane in the fivebrane background which is described by the exactly solvable SU(2)_k x U(1) world-sheet conformal field theory with large Kac-Moody level k. The D3-brane tension is extracted from the amplitude of one closed string exchange between two parallel D3-branes, and the amplitude is calculated by utilizing the open-closed string duality. The tension of the D3-brane in the background does not coincide with the one in the flat space-time even in the flat space-time limit: k -> infinity. The finite curvature effect should vanish in the flat space-time limit and only the topological effect can remain. Therefore, the deviation indicates the condensation of gravitino and/or dilatino which has been expected in the fivebrane background as a gravitational instanton.Comment: 16 pages, 1 figur

Tensor Product and Permutation Branes on the Torus

We consider B-type D-branes in the Gepner model consisting of two minimal models at k=2. This Gepner model is mirror to a torus theory. We establish the dictionary identifying the B-type D-branes of the Gepner model with A-type Neumann and Dirichlet branes on the torus.Comment: 26 page

Integrability of the N=2 boundary sine-Gordon model

We construct a boundary Lagrangian for the N=2 supersymmetric sine-Gordon model which preserves (B-type) supersymmetry and integrability to all orders in the bulk coupling constant g. The supersymmetry constraint is expressed in terms of matrix factorisations.Comment: LaTeX, 19 pages, no figures; v2: title changed, minor improvements, refs added, to appear in J. Phys. A: Math. Ge

Overall and site-specific response of the macroinvertebrate community of Swan Coastal Plain Wetlands (West Australia) to water quality gradients revealed by GF and HEA

The Swan Coastal Plain is situated along the Western Australian seaboard and accommodates a large number of permanently, seasonally and episodically flooded wetlands. Many of these wetlands are affected by eutrophication and hydrological changes. A systematic monitoring program has been conducted between 1989 and 1990 to assess the environmental status of 41 selected wetlands based on measurements of 19 physical-chemical attributes and the collection of 253 macroinvertebrate taxa samples (Davis et al. 1993). This study analysed 35 wetlands with consistent data collected in Nov 1989 and Nov 1990 by means of Gradient Forest (GF) and the Hybrid Evolutionary Algorithm (HEA). Whilst GF allows identifying macroinvertebrate taxa with the “strongest overall response” to gradients in “important” physical-chemical attributes, HEA allows to model population dynamics of the taxa depending on “important” attributes identified by GF along all 35 wetlands. HEA models are represented by IF-THEN-ELSE rules whereby IF-conditions disclose attribute thresholds that indicate changes in the species abundance across the wetlands. GF suggested different ranking of the attributes EC, TN and DIP for both years as well as different taxa assemblages for same attributes in 1989 and 1990. Since results for merged data were also different, only the year-by-year specific results have been taken into account. When inferential models have been built for the 4 species that responded “strongest” to EC, DIP and TN in 1989 and 1990 by HEA, the threshold conditions fall in the range of overall gradients of these attributes discovered by GF. GF and HEA proved to be complementary tools for identifying overall attribute gradients and species- and site-specific thresholds in complex ecological data sets. Davis, J.A., Rosich, R.S., Bradley, J.S., Growns, J.E., Schmidt, L.G. and F. Cheal, 1993. Wetlands of the Swan Coastal Plain. Vol. 6: Wetland classification on the basis of water quality and invertebrate community data. Water Authority of Western Australia