972 research outputs found
Exact gravitational plane waves and two-dimensional gravity
We discuss dynamical aspects of gravitational plane waves in Einstein theory
with massless scalar fields. The general analytic solution describes colliding
gravitational waves with constant polarization, which interact with scalar
waves and, for generic initial data, produce a spacetime singularity at the
focusing hypersurface. There is, in addition, an infinite family of regular
solutions and an intriguing static geometry supported by scalar fields. Upon
dimensional reduction, the theory can be viewed as an exactly solvable
two-dimensional gravity model. This provides a new viewpoint on the
gravitational dynamics. Finally, we comment on a simple mechanism by which
short-distance corrections in the two-dimensional model can remove the
singularity.Comment: 8 page
N=2 gauge theories and quantum phases
The partition function of general N = 2 supersymmetric SU(2) Yang-Mills
theories on a four-sphere localizes to a matrix integral. We show that in the
decompactification limit, and in a certain regime, the integral is dominated by
a saddle point. When this takes effect, the free energy is exactly given in
terms of the prepotential, , evaluated at the
singularity of the Seiberg-Witten curve where the dual magnetic variable
vanishes. We also show that the superconformal fixed point of massive
supersymmetric QCD with gauge group SU(2) is associated with the existence of a
quantum phase transition. Finally, we discuss the case of N=2* SU(2) Yang-Mills
theory and show that the theory does not exhibit phase transitions.Comment: 23 pages, 4 figure
D=2+1 N=2 Yang-Mills Theory From Wrapped Branes
We find a new solution of Type IIB supergravity which represents a collection
of D5 branes wrapped on the topologically non-trivial S^3 of the deformed
conifold geometry T^*S^3. The Type IIB solution is obtained by lifting a new
solution of D=7 SU(2)_L x SU(2)_R gauged supergravity to ten dimensions in
which SU(2)_D gauge fields in the diagonal subgroup are turned on. The
supergravity solution describes a slice of the Coulomb branch in the large N
limit of N=2 SYM in three dimensions.Comment: 19 pages, 1figure, harvmac; expanded analysis of D=4 N=2 system in
the appendix, references adde
Rotating D3-branes and QCD in three dimensions
We investigate the rotating D3-brane solution with maximum number of angular
momentum parameters. After determining the angular velocities, Hawking
temperature, ADM mass and entropy, we use this geometry to construct general
three-parameter models of non-supersymmetric pure SU(N) Yang-Mills theories in
2+1 dimensions. We calculate glueball masses in the WKB approximation and
obtain closed analytic expressions for generic values of the parameters. We
also determine the masses of Kaluza--Klein states associated with internal
parts of the ten-dimensional metric and investigate the parameter region where
some of these states are decoupled. To leading order in 1/\lambda and 1/N
(where \lambda is the 't Hooft coupling) we find a global U(1)^3 symmetry and
states with masses comparable to glueball masses, which have no counterpart in
the more familiar (finite \lambda, N) Yang-Mills theories.Comment: 14 pages, latex. v2: Reference added and typos correcte
Large N Limit of Non-Commutative Gauge Theories
Using the correspondence between gauge theories and string theory in curved
backgrounds, we investigate aspects of the large limit of non-commutative
gauge theories by considering gravity solutions with fields. We argue that
the total number of physical degrees of freedom at any given scale coincides
with the commutative case. We then compute a two-point correlation function
involving momentum components in the directions of the -field. In the UV
regime, we find that the two-point function decays exponentially with the
momentum. A calculation of Wilson lines suggests that strings cannot be
localized near the boundary. We also find string configurations that are
localized in a finite region of the radial direction. These are worldsheet
instantons.Comment: 21 pages, harvmac. Some errors in correlators corrected, minor
corrections to the Lorentzian solution
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