4,172 research outputs found
Gas of D-Branes and Hagedorn Density of BPS States
We test the prediction of a hagedorn density of BPS states which carry RR
charge in type II compactifications. We find that in certain cases they
correspond to the supersymmetric ground states for a gas of identical 0-branes.Comment: 8 pages, a minor Tex error correcte
Instantons on D-branes
We consider type IIA compactification on . We show that the instanton
subsectors of the worldvolume of 4-branes wrapped around lead to a
Hagedorn density of BPS states in accord with heterotic-type IIA duality in 6
dimensions. We also find evidence that the correct framework to understand the
results of Nakajima on the appearance of affine Kac-Moody algebras on the
cohomology of moduli space of instantons on ALE spaces is in the context of
heterotic-type IIA string duality.Comment: 11 page
U-Manifolds
We use non-perturbative U-duality symmetries of type II strings to construct
new vacuum solutions. In some ways this generalizes the F-theory vacuum
constructions. We find the possibilities of new vacuum constructions are very
limited. Among them we construct new theories with N=2 supersymmetry in
3-dimensions and (1, 1) supersymmetry in 2-dimensions.Comment: 11 pages, minor changes in references and text (version to appear in
Phys. Lett. B
Constraints on Low-Dimensional String Compactifications
We study the restrictions imposed by cancellation of the tadpoles for two,
three, and four-form gauge fields in string theory, M-theory and F-theory
compactified to two, three and four dimensions, respectively. For a large class
of supersymmetric vacua, turning on a sufficient number of strings, membranes
and three-branes, respectively, can cancel the tadpoles, and preserve
supersymmetry. However, there are cases where the tadpole cannot be removed in
this way, either because the tadpole is fractional, or because of its sign. For
M-theory and F-theory compactifications, we also explore the relation of the
membranes and three-branes to the nonperturbative space-time superpotential.Comment: 16 pages, harvma
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