922 research outputs found
Horizontal and Vertical Five-Branes in Heterotic/F-Theory Duality
We consider the heterotic string on an elliptic Calabi-Yau three-fold with
five-branes wrapping curves in the base ('horizontal' curves) of the Calabi-Yau
as well as some elliptic fibers ('vertical' curves). We show that in this
generalized set-up, where the association of the heterotic side with the
-theory side is changed relative to the purely vertical situation, the
number of five-branes wrapping the elliptic fibers still matches the
corresponding number of -theory three-branes.Comment: 21 pages harvmac, reference adde
Fourier Mukai Transforms and Applications to String Theory
We give an introductory review of Fourier-Mukai transforms and their
application to various aspects of moduli problems, string theory and mirror
symmetry. We develop the necessary mathematical background for Fourier-Mukai
transforms such as aspects of derived categories and integral functors as well
as their relative version which becomes important for making precise the notion
of fiberwise T-duality on elliptic Calabi-Yau threefolds. We discuss various
applications of the Fourier-Mukai transform to D-branes on Calabi-Yau manifolds
as well as homological mirror symmetry and the construction of vector bundles
for heterotic string theory.Comment: 52 pages. To appear in Rev. R. Acad. Cienc. Exactas Fis. Nat. Ser. A
Mat. Minor changes, reference of conjecture in section 7.5 changed,
references update
Anomalous D-Brane Charge in F-Theory Compactifications
Tadpole cancellation in F-theory on an elliptic Calabi-Yau fourfold demands some spacetime-filling three-branes (points in ). If moved to
the discriminant surface, which supports the gauge group, and dissolved into a
finite size instanton, the second Chern class of the corresponding bundle
is expected to give a compensating contribution. However the dependence of
D-brane charge on the geometry of and on the embedding gives
a correction to . We show how this is reconciled by considering the
torsion sheaf and discuss some integrality issues related to global
properties of as well as the moduli space of this object.Comment: 11 pages, harvmac, reference adde
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