15,888 research outputs found
Comments on Non-Supersymmetric Orientifolds at Strong Coupling
We consider several properties of a set of anti-D-branes in the presence
of orientifold -planes in type II theory. This system breaks all the
supersymmetries of the theory, but is free of tachyons. In particular, we
center on the case of a single anti-D-brane stuck at a negatively charged
orientifold -plane, and study its strong coupling behaviour for .
Interestingly enough, as the coupling increases the system undergoes a phase
transition where an additional antibrane is created. We conclude with some
remarks on the limit of large number of antibranes on top of orientifold
planes.Comment: 14 pages, Latex. Orientifold-antibrane short distance interaction
corrected, references adde
Brane Configurations for Branes at Conifolds
We study the T duality between a set of type IIB D3 branes atnon-orbifold
threefold singularities, and type IIA configurations of D4 branes stretched
between relatively rotated NS fivebranes. The four-dimensional N=1 field
theories on the D3 brane world-volume can be easily described using the IIA
brane configuration. These models include families of chiral theories
continuously connected to the theories appearing in brane box models (or D3
branes at orbifold singularities). We propose that phase transitions in the
K\"ahler moduli space of the singularity are related to the crossing of rotated
NS fivebranes in the T dual picture, and thus to Seiberg's duality in one of
the gauge factors. We also comment on the inclusion of orientifold planes in
the IIA brane picture.Comment: 34 pages, Latex, 7 eps figures. Several comments added, and important
clarifications concerning Seiberg dualit
Wrapped fluxbranes
We consider the construction of fluxbranes in certain curved geometries,
generalizing the familiar construction of the Melvin fluxtube as a quotient of
flat space. The resulting configurations correspond to fluxbranes wrapped on
cycles in curved spaces. The non-trivial transverse geometry leads in some
instances to solutions with asymptotically constant dilaton profiles. We
describe explicitly several supersymmetric solutions of this kind. The
solutions inherit some properties from their flat space cousins, like flux
periodicity. Interestingly type IIA/0A fluxbrane duality holds near the core of
these fluxbranes, but does not persist in the asymptotic region, precisely
where it would contradict perturbative inequivalence of IIA/0A theories.Comment: 22 pages, latex, no figures. Added reference
Lessons from the Andean Community Integration. Jean Monnet/Robert Schuman Paper Series. Vol. 6, No. 12 June 2006
[From the Introduction]. Ever since it was born in the sixties, the Andean Regional Integration Process has attempted to become a strategy to promote a harmonious and balanced development among the Andean Countries. This paper has tree mains goals: (a) To explain and analyse the theoretical concept of the Andean New Regionalism in the framework of Latin American region in a comparative perspective with the European Model of Regional Integration; (b) To show the coexistence of two different regional integration models. Where the dominating one during the sixties was known as old regionalism, and the other that is currently being used is known as new regionalism, and (c) To analyse the way in which this coexistence appears to be an obstacle for the Andean countries to define their regional integration model and to advance toward their main goal: the balanced and harmonious development of each and every country member
On the spectrum of a Hamiltonian defined on su_q(2) and quantum optical models
Analytical expressions are given for the eigenvalues and eigenvectors of a
Hamiltonian with su_q(2) dynamical symmetry. The relevance of such an operator
in Quantum Optics is discussed. As an application, the ground state energy in
the Dicke model is studied through su_q(2) perturbation theory.Comment: 11 pages, LaTeX, content change
External fluctuations in front dynamics with inertia: The overdamped limit
We study the dynamics of fronts when both inertial effects and external
fluctuations are taken into account. Stochastic fluctuations are introduced as
multiplicative noise arising from a control parameter of the system. Contrary
to the non-inertial (overdamped) case, we find that important features of the
system, such as the velocity selection picture, are not modified by the noise.
We then compute the overdamped limit of the underdamped dynamics in a more
careful way, finding that it does not exhibit any effect of noise either. Our
result poses the question as to whether or not external noise sources can be
measured in physical systems of this kind.Comment: 4 pages, 1 figure, accepted for publication in European Physical
Journal
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