21,482 research outputs found
Massive Gravity on a Non-extremal Brane
We consider a brane world scenario which arises as the near-horizon region of
a non-extremal D5-brane. There is a quasi-localized massive graviton mode, as
well as harmonic modes of higher mass which are bound to the brane to a lesser
degree. Lorentz invariance is slightly broken, which may have observable
effects due to the leakage of the metastable graviton states into the bulk.
Unlike a brane world arising from an extremal D5-brane, there is no mass gap.
We also find that a brane world arising from a non-extremal M5/M5-brane
intersection has the same graviton dynamics as that of a non-extremal D5-brane.
This is evidence that a previously conjectured duality relation between the
dual quantum field theories of each p-brane background may hold away from
extremality.Comment: 10 pages, 4 figures, LaTe
Ultimate Fate of Constrained Voters
We determine the ultimate fate of individual opinions in a
socially-interacting population of leftists, centrists, and rightists. In an
elemental interaction between agents, a centrist and a leftist can become both
centrists or both become leftists with equal rates (and similarly for a
centrist and a rightist). However leftists and rightists do not interact. This
interaction step between pairs of agents is applied repeatedly until the system
can no longer evolve. In the mean-field limit, we determine the exact
probability that the system reaches consensus (either leftist, rightist, or
centrist) or a frozen mixture of leftists and rightists as a function of the
initial composition of the population. We also determine the mean time until
the final state is reached. Some implications of our results for the ultimate
fate in a limit of the Axelrod model are discussed.Comment: 10 pages, 6 figures, 2-column revtex format; for submission to J.
Phys. A. Final version for JPA; very minor change
S^1-wrapped D3-branes on Conifolds
We construct a D3-brane wrapped on S^1, which is fibred over the resolved
conifold as its transverse space. Whereas a fractional D3-brane on the resolved
conifold is not supersymmetric and has a naked singularity, our solution is
supersymmetric and regular everywhere. We also consider an -wrapped
D3-brane on the resolved cone over T^{1,1}/Z_2, as well as on the deformed
conifold. In the former case, we obtain a regular supergravity dual to a
certain four-dimensional field theory whose Lorentz and conformal symmetries
are broken in the IR region and restored in the UV limit.Comment: Latex, 14 pages, minor correction
Penrose Limits of Non-standard Brane Intersections
The non-standard intersection of two 5-branes and a string can give rise to
AdS_3\times S^3\times S^3\times S^1. We consider the Penrose limit of this
geometry and study the supersymmetry of the resulting pp-wave solution. There
is a one-parameter family of Penrose limits associated with the orthogonal
rotation of the two foliating circles within the two 3-spheres. Supernumerary
Killing spinors arise only when the rotation angle is 45 degrees, for which
case we obtain the corresponding light-cone string action that has
linearly-realised supersymmetry. We also obtain Penrose limits of other
non-standard intersections that give rise to the product of AdS_3 or AdS_2 and
two spheres. The resulting pp-waves are supported by multiple constant field
strengths.Comment: Latex, 15 pages, references adde
Non-singular Twisted S-branes From Rotating Branes
We show that rotating p-brane solutions admit an analytical continuation to
become twisted Sp-branes. Although a rotating p-brane has a naked singularity
for large angular momenta, the corresponding S-brane configuration is regular
everywhere and exhibits a smooth bounce between two phases of Minkowski
spacetime. If the foliating hyperbolic space of the transverse space is of even
dimension, such as for the twisted SM5-brane, then for an appropriate choice of
parameters the solution smoothly flows from a warped product of two-dimensional
de Sitter spacetime, five-dimensional Euclidean space and a hyperbolic 4-space
in the infinite past to Minkowski spacetime in the infinite future. We also
show that non-singular S-Kerr solutions can arise from higher-dimensional Kerr
black holes, so long as all (all but one) angular momenta are non-vanishing for
even (odd) dimensions.Comment: Latex, 20 page
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