Comments on Non-Supersymmetric Orientifolds at Strong Coupling

We consider several properties of a set of anti-D$p$-branes in the presence of orientifold $p$-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$p$-brane stuck at a negatively charged orientifold $p$-plane, and study its strong coupling behaviour for $p=2,3,4$. 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