2,036 research outputs found
Pseudo-supersymmetry, Consistent Sphere Reduction and Killing Spinors for the Bosonic String
Certain supergravity theories admit a remarkable consistent dimensional
reduction in which the internal space is a sphere. Examples include type IIB
supergravity reduced on S^5, and eleven-dimensional supergravity reduced on S^4
or S^7. Consistency means that any solution of the dimensionally-reduced theory
lifts to give a solution in the higher dimension. Although supersymmetry seems
to play a role in the consistency of these reductions, it cannot be the whole
story since consistent sphere reductions of non-supersymmetric theories are
also known, such as the reduction of the effective action of the bosonic string
in any dimension D on either a 3-sphere or a (D-3)-sphere, retaining the gauge
bosons of SO(4) or SO(D-2) respectively. We show that although there is no
supersymmetry, there is nevertheless a natural Killing spinor equation for the
D-dimensional bosonic string. A projection of the full integrability condition
for these Killing spinors gives rise to the bosonic equations of motion (just
as happens in the supergravity examples). Thus it appears that by extending the
notion of supersymmetry to "pseudo-supersymmetry" in this way, one may be able
to obtain a broader understanding of a relation between Killing spinors and
consistent sphere reductions.Comment: Latex, 15 page
Non-equilibrium dynamics of simple spherical spin models
We investigate the non-equilibrium dynamics of spherical spin models with
two-spin interactions. For the exactly solvable models of the d-dimensional
spherical ferromagnet and the spherical Sherrington-Kirkpatrick model the
asymptotic dynamics has for large times and for large waiting times the same
formal structure. In the limit of large waiting times we find in both models an
intermediate time scale, scaling as a power of the waiting time with an
exponent smaller than one, and thus separating the time-translation invariant
short-time dynamics from the aging regime. It is this time scale on which the
fluctuation-dissipation regime is violated. Aging in these models is similar to
that observed in spin glasses at the level of correlation functions, but
different at the level of response functions, and thus different at the level
of experimentally accessible quantities like the thermoremanent magnetization.Comment: 8 pages, 1 eps figur
AdS Wormholes
We obtain a large class of smooth Lorentzian p-brane wormholes in
supergravities in various dimensions. They connect two asymptotically flat
spacetimes. In cases where there is no dilaton involved in the solution, the
wormhole can connect an AdS_n\times S^m in one asymptotic region to a flat
spacetime in the other. We obtain explicit examples for (n,m)=(4,7), (7,4),
(5,5), (3,3), (3,2). These geometries correspond to field theories with UV
conformal fixed points, and they undergo decompactification in the IR region.
In the case of AdS_3, we compute the central charge of the corresponding
conformal field theory.Comment: 20 pages, references adde
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