88 research outputs found
Gravitational Instantons and Fluxes from M/F-theory on Calabi-Yau fourfolds
We compactify four-dimensional N=1 gauged supergravity theories on a circle
including fluxes for shift-symmetric scalars. Four-dimensional Taub-NUT
gravitational instantons universally correct the three-dimensional
superpotential in the absence of fluxes. In the presence of fluxes these
Taub-NUT instanton contributions are no longer gauge-invariant. Invariance can
be restored by gauge instantons on top of Taub-NUT instantons. We establish the
embedding of this scenario into M-theory. Circle fluxes and gaugings arise from
a restricted class of M-theory four-form fluxes on a resolved Calabi-Yau
fourfold. The M5-brane on the base of the elliptic fourfold dualizes into the
universal Taub-NUT instanton. In the presence of fluxes this M5-brane is
anomalous. We argue that anomaly free contributions arise from involved
M5-brane geometries dual to gauge-instantons on top of Taub-NUT instantons.
Adding a four-dimensional superpotential to the gravitational instanton
corrections leads to three-dimensional Anti-de Sitter vacua at stabilized
compactification radius. We comment on the possibility to uplift these M-theory
vacua, and to tunnel to four-dimensional F-theory vacua.Comment: 47 pages, 2 figure
Supergravity Solution of Intersecting Branes and AdS/CFT with Flavor
We construct the supergravity solution for fully localized D2/D6
intersection. The near horizon limit of this solution is the supergravity dual
of supersymmetric Yang-Mills theory in 2+1 dimensions with flavor. We use this
solution to formulate mirror symmetry of 2+1 dimensional gauge theories in the
language of AdS/CFT correspondence. We also construct the supergravity dual of
a non-commutative gauge theory with fundamental matter.Comment: 17 Pages, 2 figures, references added. Minor corrections to eqs (5.3)
and (5.4
Numerical Investigation of Monopole Chains
We present numerical results for chains of SU(2) BPS monopoles constructed
from Nahm data. The long chain limit reveals an asymmetric behavior transverse
to the periodic direction, with the asymmetry becoming more pronounced at
shorter separations. This analysis is motivated by a search for semiclassical
finite temperature instantons in the 3D SU(2) Georgi-Glashow model, but it
appears that in the periodic limit the instanton chains either have
logarithmically divergent action or wash themselves out.Comment: 14 pages, 6 figures; v2 minor changes, published versio
The Viscosity Bound Conjecture and Hydrodynamics of M2-Brane Theory at Finite Chemical Potential
Kovtun, Son and Starinets have conjectured that the viscosity to entropy
density ratio is always bounded from below by a universal multiple of
i.e., for all forms of matter. Mysteriously, the
proposed viscosity bound appears to be saturated in all computations done
whenever a supergravity dual is available. We consider the near horizon limit
of a stack of M2-branes in the grand canonical ensemble at finite R-charge
densities, corresponding to non-zero angular momentum in the bulk. The
corresponding four-dimensional R-charged black hole in Anti-de Sitter space
provides a holographic dual in which various transport coefficients can be
calculated. We find that the shear viscosity increases as soon as a background
R-charge density is turned on. We numerically compute the few first corrections
to the shear viscosity to entropy density ratio and surprisingly
discover that up to fourth order all corrections originating from a non-zero
chemical potential vanish, leaving the bound saturated. This is a sharp signal
in favor of the saturation of the viscosity bound for event horizons even in
the presence of some finite background field strength. We discuss implications
of this observation for the conjectured bound.Comment: LaTeX, 26+1 Pages, 4 Figures, Version 2: references adde
Constructing Self-Dual Strings
We present an ADHMN-like construction which generates self-dual string
solutions to the effective M5-brane worldvolume theory from solutions to the
Basu-Harvey equation. Our construction finds a natural interpretation in terms
of gerbes, which we develop in some detail. We also comment on a possible
extension to stacks of multiple M5-branes.Comment: 1+19 pages, presentation improved, minor corrections, published
versio
Gibbons-Hawking M-branes
We present new M2 and M5-brane solutions in M-theory based on transverse
Gibbons-Hawking spaces. These solutions provide realizations of fully localized
type IIA D2/D6 and NS5/D6 brane intersections. One novel feature of these
solutions is that the metric functions depend on more than two transverse
coordinates (unlike all the other previous known solutions). All the solutions
have eight preserved supersymmetries and the world-volume theories of the
NS5-branes are new non-local, non-gravitational, six dimensional, T-dual little
string theories with eight supersymmetries. We discuss the limits in which the
dynamics of the D2 and NS5-branes decouple from the bulk for these solutions.Comment: 32 pages, 7 figures, few sentences added, a couple of typos
corrected, to appear in JHE
Quantized Nambu-Poisson Manifolds in a 3-Lie Algebra Reduced Model
We consider dimensional reduction of the Bagger-Lambert-Gustavsson theory to
a zero-dimensional 3-Lie algebra model and construct various stable solutions
corresponding to quantized Nambu-Poisson manifolds. A recently proposed Higgs
mechanism reduces this model to the IKKT matrix model. We find that in the
strong coupling limit, our solutions correspond to ordinary noncommutative
spaces arising as stable solutions in the IKKT model with D-brane backgrounds.
In particular, this happens for S^3, R^3 and five-dimensional Neveu-Schwarz
Hpp-waves. We expand our model around these backgrounds and find effective
noncommutative field theories with complicated interactions involving
higher-derivative terms. We also describe the relation of our reduced model to
a cubic supermatrix model based on an osp(1|32) supersymmetry algebra.Comment: 22 page
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