Candidates for anti-de Sitter Horizons

We find, from the toric description of the moduli space of D3-branes on non-compact six-dimensional singularities \C^3/\Z_3 and \C^3/\Z_5 in the blown-down limit, the four-dimensional bases on which these singular spaces are complex cones, and prove the existence of K\"ahler-Einstein metrics on these four-dimensional bases. This shows, in particular, that one can use the horizons obtained from these base spaces by a U(1)-foliation as compact parts of the target space for Type-IIB string theory with \ads{5} in the context of the AdS-CFT correspondence.Comment: 16 pages, LATEX2e. Uses times, eepic, amsmath and amssym

Fractional Branes on a Non-compact Orbifold

Fractional branes on the non-compact orbifold \C^3/\Z_5 are studied. First, the boundary state description of the fractional branes are obtained. The open-string Witten index calculated using these states reproduces the adjacency matrix of the quiver of $\Z_5$. Then, using the toric crepant resolution of the orbifold \C^3/\Z_5 and invoking the local mirror principle, B-type branes wrapped on the holomorphic cycles of the resolution are studied. The boundary states corresponding to the five fractional branes are identified as bound states of BPS D-branes wrapping the 0-, 2- and 4-cycles in the exceptional divisor of the resolution of \C^3/\Z_5.Comment: Latex2e, 25 pages, typos corrected, minor modifications, version to appear in JHE

Beta-gamma system, pure spinors and Hilbert series of arc spaces

Algorithms are presented for calculating the partition function of constrained beta-gamma systems in terms of the generating functions of the individual fields of the theory, the latter obtained as the Hilbert series of the arc space of the algebraic variety defined by the constraint. Examples of a beta-gamma system on a complex surface with an $A_1$ singularity and pure spinors are worked out and compared with existing results.Comment: 19 pages; sections 2.2, 4.2 and 5, revised for clarity; Macaulay2 code for pure spinors added in appendix A; acknowledgments added; version to appear in JHE