67 research outputs found
The Acceleration of the Universe, a Challenge for String Theory
Recent astronomical observations indicate that the universe is accelerating.
We argue that generic quintessence models that accommodate the present day
acceleration tend to accelerate eternally. As a consequence the resulting
spacetimes exhibit event horizons. Hence, quintessence poses the same problems
for string theory as asymptotic de Sitter spaces.Comment: JHEP, LaTeX, 12 pages, 4 figures. Added a reference, corrected typo
Phase space polarization and the topological string: a case study
We review and elaborate on our discussion in hep-th/0606112 on the interplay
between the target space and the worldsheet description of the open topological
string partition function, for the example of the conifold. We discuss the
appropriate phase space and canonical form for the system. We find a map
between choices of polarization and the worldsheet description, based on which
we study the behavior of the partition function under canonical
transformations.Comment: 18 pages, invited review for MPL
Instanton Counting and Chern-Simons Theory
The instanton partition function of N=2, D=4 SU(2) gauge theory is obtained
by taking the field theory limit of the topological open string partition
function, given by a Chern-Simons theory, of a CY3-fold. The CY3-fold on the
open string side is obtained by geometric transition from local F_0 which is
used in the geometric engineering of the SU(2) theory. The partition function
obtained from the Chern-Simons theory agrees with the closed topological string
partition function of local F_0 proposed recently by Nekrasov. We also obtain
the partition functions for local F_1 and F_2 CY3-folds and show that the
topological string amplitudes of all local Hirzebruch surfaces give rise to the
same field theory limit. It is shown that a generalization of the topological
closed string partition function whose field theory limit is the generalization
of the instanton partition function, proposed by Nekrasov, can be determined
easily from the Chern-Simons theory.Comment: 39 pages, references added, typos corrected, cosmetic change
Moduli Potentials in Type IIA Compactifications with RR and NS Flux
We describe a simple class of type IIA string compactifications on Calabi-Yau
manifolds where background fluxes generate a potential for the complex
structure moduli, the dilaton, and the K\"ahler moduli. This class of models
corresponds to gauged N=2 supergravities, and the potential is completely
determined by a choice of gauging and by data of the N=2 Calabi-Yau model - the
prepotential for vector multiplets and the quaternionic metric on the
hypermultiplet moduli space. Using mirror symmetry, one can determine many
(though not all) of the quantum corrections which are relevant in these models.Comment: 30 pages, 2 figures; v2: minor change
The toroidal block and the genus expansion
We study the correspondence between four-dimensional supersymmetric gauge
theories and two-dimensional conformal field theories in the case of N=2* gauge
theory. We emphasize the genus expansion on the gauge theory side, as obtained
via geometric engineering from the topological string. This point of view
uncovers modular properties of the one-point conformal block on a torus with
complexified intermediate momenta: in the large intermediate weight limit, it
is a power series whose coefficients are quasi-modular forms. The all-genus
viewpoint that the conformal field theory approach lends to the topological
string yields insight into the analytic structure of the topological string
partition function in the field theory limit.Comment: 36 page
Evidence for Winding States in Noncommutative Quantum Field Theory
We study noncommutative field theories at finite temperature to learn more
about the degrees of freedom in the non-planar sector of these systems. We find
evidence for winding states. At temperatures for which the thermal wavelength
is smaller than the noncommutativity scale, there is a drastic reduction of the
degrees of freedom in the non-planar sector. In this regime, the non-planar
sector has thermodynamics resembling that of a 1+1 dimensional field theory.Comment: 15 pages, 3 figures. Typos corrected and minor clarifications adde
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