746 research outputs found
String Solitons
We review the status of solitons in superstring theory, with a view to
understanding the strong coupling regime. These {\it solitonic} solutions are
non-singular field configurations which solve the empty-space low-energy field
equations (generalized, whenever possible, to all orders in ), carry a
non-vanishing topological "magnetic" charge and are stabilized by a topological
conservation law. They are compared and contrasted with the {\it elementary}
solutions which are singular solutions of the field equations with a
-model source term and carry a non-vanishing Noether "electric" charge.
In both cases, the solutions of most interest are those which preserve half the
spacetime supersymmetries and saturate a Bogomol'nyi bound. They typically
arise as the extreme mass=charge limit of more general two-parameter solutions
with event horizons. We also describe the theory {\it dual} to the fundamental
string for which the roles of elementary and soliton solutions are
interchanged. In ten spacetime dimensions, this dual theory is a superfivebrane
and this gives rise to a string/fivebrane duality conjecture according to which
the fivebrane may be regarded as fundamental in its own right, with the
strongly coupled string corresponding to the weakly coupled fivebrane and
vice-versa. After compactification to four spacetime dimensions, the fivebrane
appears as a magnetic monopole or a dual string according as it wraps around
five or four of the compactified dimensions. This gives rise to a
four-dimensional string/string duality conjecture which subsumes a
Montonen-Olive type duality in that the magnetic monopoles of the fundamental
string correspond to the electric winding states of the dual string. This leads
to a {\it duality of dualities} whereby under string/string duality the the
strong/weak coupling -duality trades places with the minimum/maximum length
-duality. Since these magnetic monopoles are extreme black holes, a
prediction of -duality is that the corresponding electric massive states of
the fundamental string are also extreme black holes.Comment: 150 pages, TeX, submitted to Physics Reports, 3 figures available on
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Phase transitions and critical behavior of black branes in canonical ensemble
We study the thermodynamics and phase structure of asymptotically flat
non-dilatonic as well as dilatonic black branes in a cavity in arbitrary
dimensions (). We consider the canonical ensemble and so the charge inside
the cavity and the temperature at the wall are fixed. We analyze the stability
of the black brane equilibrium states and derive the phase structures. For the
zero charge case we find an analog of Hawking-Page phase transition for these
black branes in arbitrary dimensions. When the charge is non-zero, we find that
below a critical value of the charge, the phase diagram has a line of
first-order phase transition in a certain range of temperatures which ends up
at a second order phase transition point (critical point) as the charge attains
the critical value. We calculate the critical exponents at that critical point.
Although our discussion is mainly concerned with the non-dilatonic branes, we
show how it easily carries over to the dilatonic branes as well.Comment: 37 pages, 6 figures, the validity of using the effective action
discussed, references adde
L'école du terrain ou l'interdisciplinarité de chantier : un hybride en cours de construction
Vanishing Cosmological Constant by Gravitino-Dressed Compactification of 11D Supergravity
We consider compactifications induced by the gravitino field of eleven
dimensional supergravity. Such compactifications are not trivial in the sense
that the gravitino profiles are not related to pure bosonic ones by means of a
supersymmetry transformation. The basic property of such backgrounds is that
they admit -torsion although they have vanishing Riemann tensor. Thus,
these backgrounds may be considered also as solutions of the teleparallel
formulation of supergravity. We construct two classes of solutions, one with
both antisymmetric three-form field, gravity and gravitino and one with only
gravity and gravitino. In these classes of solutions, the internal space is a
parallelized compact manifold, so that it does not inherit any cosmological
constant to the external spacetime. The latter turns out to be flat Minkowski
in the maximally symmetric case. The elimination of the cosmological constant
in the spontaneously compactified supergravity seems to be a generic property
based on the trading of the cosmological constant for parallelizing torsion.Comment: 17 pages, no figure
Linearized gravity as a gauge theory
We discuss linearized gravity from the point of view of a gauge theory. In
(3+1)-dimensions our analysis allows to consider linearized gravity in the
context of the MacDowell-Mansouri formalism. Our observations may be of
particular interest in the strong-weak coupling duality for linearized gravity,
in Randall-Sundrum brane world scenario and in Ashtekar formalism.Comment: Latex, 13 page
BPS preons and the AdS-M-algebra
We present here the AdS generalization of BPS preons, which were introduced
as the hypothetical constituents of M-theory preserving all but one
supersymmetries. Our construction, suggested by the relation of `lower
dimensional preons' with higher spin theories, can be considered as a
deformation of the M-algebraic description of the single supersymmetry broken
by a preon, and provides another reason to identify the AdS generalization of
the M-algebra, which we call the AdS-M-algebra, with osp(1|32).Comment: Plain latex, no figures, 19 pages minor corrections, one ref. added,
as published in JHEP 04 (2008) 06
New angles on D-branes
A low-energy background field solution is presented which describes several
D-membranes oriented at angles with respect to one another. The mass and charge
densities for this configuration are computed and found to saturate the BPS
bound, implying the preservation of one-quarter of the supersymmetries.
T-duality is exploited to construct new solutions with nontrivial angles from
the basic one.Comment: Latex, 12 pages, still no figures, references update
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