67 research outputs found
Neveu-Schwarz Five-Branes And Matrix String Theory On K3
The Matrix theory description of Type IIA string theory on a compact K3
surface as the theory of Neveu-Schwarz five-branes on is
analyzed. The full multiplet of space-time BPS states is identified in the
five-brane world-volume as fluxes.Comment: harvmac, 12 pages, some changes in the T-duality on K3 sectio
The Coulomb Branch of (4,4) Supersymmetric Field Theories in Two Dimensions
We study (4,4) supersymmetric field theories in two dimensions with a one
dimensional Coulomb branch. These theories have applications in string theory.
Our analysis explains the known relation between groups and modular
invariants of affine SU(2).Comment: 18 pages, minor change
Fractional Branes and Boundary States in Orbifold Theories
We study the D-brane spectrum of N=2 string orbifold theories using the
boundary state formalism. The construction is carried out for orbifolds with
isolated singularities, non-isolated singularities and orbifolds with discrete
torsion. Our results agree with the corresponding K-theoretic predictions when
they are available and generalize them when they are not. This suggests that
the classification of boundary states provides a sort of "quantum K-theory"
just as chiral rings in CFT provide "quantum" generalizations of cohomology. We
discuss the identification of these states with D-branes wrapping holomorphic
cycles in the large radius limit of the CFT moduli space. The example C^3/Z_3
is worked out in full detail using local mirror symmetry techniques. We find a
precise correspondence between fractional branes at the orbifold point and
configurations of D-branes described by vector bundles on the exceptional P^2
cycle.Comment: 48 pages, Harvmac, 3 postscript figures, references and a note adde
Spectral Covers, Charged Matter and Bundle Cohomology
We consider four dimensional heterotic compactifications on smooth elliptic
Calabi-Yau threefolds. Using spectral cover techniques, we study bundle
cohomology groups corresponding to charged matter multiplets. The analysis
shows that in generic situations, the resulting charged matter spectrum is
stable under deformations of the vector bundle.Comment: 17 pages, harvmac; minor change
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