13,204 research outputs found
The Free Energy of N=4 Super-Yang-Mills and the AdS/CFT Correspondence
We compute the high-temperature limit of the free energy for four-dimensional
N=4 supersymmetric SU(N_c) Yang-Mills theory. At weak coupling we do so for a
general ultrastatic background spacetime, and in the presence of slowly-varying
background gauge fields. Using Maldacena's conjectured duality, we calculate
the strong-coupling large-N_c expression for the special case that the
three-space has constant curvature. We compare the two results paying
particular attention to curvature corrections to the leading order expressions.Comment: 26 pages.Minor corrections to eqs.(19),(21). Results and conclusions
unchanged. References adde
Sculpting the Extra Dimensions: Inflation from Codimension-2 Brane Back-reaction
We construct an inflationary model in 6D supergravity that is based on
explicit time-dependent solutions to the full higher-dimensional field
equations, back-reacting to the presence of a 4D inflaton rolling on a
space-filling codimension-2 source brane. Fluxes in the bulk stabilize all
moduli except the `breathing' modulus (that is generically present in
higher-dimensional supergravities). Back-reaction to the inflaton roll causes
the 4D Einstein-frame on-brane geometry to expand, a(t) ~ t^p, as well as
exciting the breathing mode and causing the two off-brane dimensions to expand,
r(t) ~ t^q. The model evades the general no-go theorems precluding 4D de Sitter
solutions, since adjustments to the brane-localized inflaton potential allow
the power p to be dialed to be arbitrarily large, with the 4D geometry becoming
de Sitter in the limit p -> infinity (in which case q = 0). Slow-roll solutions
give accelerated expansion with p large but finite, and q = 1/2. Because the
extra dimensions expand during inflation, the present-day 6D gravity scale can
be much smaller than it was when primordial fluctuations were generated -
potentially allowing TeV gravity now to be consistent with the much higher
gravity scale required at horizon-exit for observable primordial gravity waves.
Because p >> q, the 4 on-brane dimensions expand more quickly than the 2
off-brane ones, providing a framework for understanding why the observed four
dimensions are presently so much larger than the internal two. If uplifted to a
10D framework with 4 dimensions stabilized, the 6D evolution described here
could describe how two of the six extra dimensions evolve to become much larger
than the others, as a consequence of the enormous expansion of the 4 large
dimensions we can see.Comment: 27 pages + appendices, 2 figure
Cosmology and Static Spherically Symmetric solutions in D-dimensional Scalar Tensor Theories: Some Novel Features
We consider scalar tensor theories in D-dimensional spacetime, D \ge 4. They
consist of metric and a non minimally coupled scalar field, with its non
minimal coupling characterised by a function. The probes couple minimally to
the metric only. We obtain vacuum solutions - both cosmological and static
spherically symmetric ones - and study their properties. We find that, as seen
by the probes, there is no singularity in the cosmological solutions for a
class of functions which obey certain constraints. It turns out that for the
same class of functions, there are static spherically symmetric solutions which
exhibit novel properties: {\em e.g.} near the ``horizon'', the gravitational
force as seen by the probe becomes repulsive.Comment: Revtex. 21 pages. Version 2: More references added. Version 3: Issues
raised by the referee are addressed. Results unchanged. Title modified; a new
subsection and more references added. Verison to appear in Physical Review
Searching for the dual of the Maxwell-Chern-Simons model minimally coupled to dynamical U(1) charged matter
The possibility of dual equivalence between the self-dual and the
Maxwell-Chern-Simons (MCS) models when the latter is coupled to dynamical, U(1)
fermionic charged matter is examined. The proper coupling in the self-dual
model is then disclosed using the iterative gauge embedding approach. We found
that the self-dual potential needs to couple directly to the Chern-Kernel of
the source in order to establish this equivalence besides the need for a
self-interaction term to render the matter sector unchanged.Comment: 4 pages, RevTeX, new references, accepted for publication on Phys.
Lett.
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