3,520 research outputs found
Moonshine in Fivebrane Spacetimes
We consider type II superstring theory on and study perturbative BPS states in the near-horizon
background of two Neveu-Schwarz fivebranes whose world-volume wraps the factor. These states are counted by the spacetime helicity
supertrace which we evaluate. We find a simple expression for
in terms of the completion of the mock modular form
that has appeared recently in studies of the decomposition of
the elliptic genus of K3 surfaces into characters of the N=4 superconformal
algebra and which manifests a moonshine connection to the Mathieu group
.Comment: 32 page
String Islands
We discuss string theories with small numbers of non-compact moduli and
describe constructions of string theories whose low-energy limit is described
by various pure supergravity theories. We also construct a D=4,N=4
compactification of type II string theory with 34 vector fields.Comment: An erroneous example removed. We thank Massimo Bianchi and Cumrun
Vafa for pointing out this erro
An Uplifting Discussion of T-Duality
It is well known that string theory has a T-duality symmetry relating circle
compactifications of large and small radius. This symmetry plays a foundational
role in string theory. We note here that while T-duality is order two acting on
the moduli space of compactifications, it is order four in its action on the
conformal field theory state space. More generally, involutions in the Weyl
group which act at points of enhanced symmetry have canonical lifts
to order four elements of , a phenomenon first investigated by J. Tits in
the mathematical literature on Lie groups and generalized here to conformal
field theory. This simple fact has a number of interesting consequences. One
consequence is a reevaluation of a mod two condition appearing in asymmetric
orbifold constructions. We also briefly discuss the implications for the idea
that T-duality and its generalizations should be thought of as discrete gauge
symmetries in spacetime.Comment: 47 pages, claims regarding valued cocycles remove
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