901 research outputs found
Conifold Cosmologies in IIA String Theory
We discuss the extension of our recent work hep-th/0410272, hep-th/0410273 to
general conifold transitions and type-IIA string theory.Comment: 8 pages, 4 figures, contributed to the proceedings of the 37-th
International Symposium Ahrenshoop, Berlin, August 23-27, 200
Critical Wilson Lines in Toroidal Compactifications of Heteroric Strings
Critical values of Wilson lines and general background fields for toroidal
compactifications of heterotic string theories are constructed systematically
using Dynkin diagrams.Comment: 32 pages, LATE
Special geometry, black holes and Euclidean supersymmetry
We review recent developments in special geometry and explain its role in the
theory of supersymmetric black holes. To make this article self-contained, a
short introduction to black holes is given, with emphasis on the laws of black
hole mechanics and black hole entropy. We also summarize the existing results
on the para-complex version of special geometry, which occurs in Euclidean
supersymmetry. The role of real coordinates in special geometry is illustrated,
and we briefly indicate how Euclidean supersymmetry can be used to study
stationary black hole solutions via dimensional reduction over time.
This article is an updated and substantially extended version of the previous
review article `New developments in special geometry', hep-th/0602171.Comment: 39 pages, Contribution to the Handbook on Pseudo-Riemannian Geometry
and Supersymmtry, ed. V. Corte
Duality and black hole partition functions
Supersymmetric black holes provide an excellent theoretical laboratory to
test ideas about quantum gravity in general and black hole entropy in
particular. When four-dimensional supergravity is interpreted as the low-energy
approximation of ten-dimensional string theory or eleven-dimensional M-theory,
one has a microscopic description of the black hole which allows one to count
microstates and to compare the result to the macroscopic (geometrical) entropy.
Recently it has been conjectured that there is a very direct connection between
the partition function of the topological string and a partition function for
supersymmetric black holes. We review this idea and propose a modification
which makes it compatible with electric-magnetic duality.Comment: 5 pages, based on talk given at the 11th Marcel Grossmann meeting,
Berlin, July 23-29, 200
New developments in special geometry
We review recent developments in special geometry, emphasizing the role of
real coordinates. In the first part we discuss the para-complex geometry of
vector and hypermultiplets in rigid Euclidean N=2 supersymmetry. In the second
part we study the variational principle governing the near horizon limit of BPS
black holes in matter-coupled N=2 supergravity and observe that the black hole
entropy is the Legendre transform of the Hesse potential encoding the geometry
of the scalar fields.Comment: 27 pages, contributed to the Handbook on Pseudo-Riemannian Geometry
and Supersymmetr
Topological Transitions and Enhancon-like Geometries in Calabi-Yau Compactifications of M-Theory
We study the impact of topological phase transitions of the internal
Calabi-Yau threefold on the space-time geometry of five-dimensional extremal
black holes and black strings. For flop transitions and SU(2) gauge symmetry
enhancement we show that solutions can always be continued and that the
behaviour of metric, gauge fields and scalars can be characterized in a model
independent way. Then we look at supersymmetric solutions which describe naked
singularities rather than geometries with a horizon. For black strings we show
that the solution cannot become singular as long as the scalar fields take
values inside the Kahler cone. For black holes we establish the same result for
the elliptic fibrations over the Hirzebruch surfaces F_0, F_1, F_2. These three
models exhibit a behaviour similar to the enhancon, since one runs into SU(2)
enhancement before reaching the apparent singularity. Using the proper
continuation inside the enhancon radius one finds that the solution is regular.Comment: 7 page
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