Stable p-branes in Chern-Simons AdS supergravities

We construct static codimension-two branes in any odd dimension D, with negative cosmological constant, and show that they are exact solutions of Chern-Simons (super)gravity theory for (super)AdS coupled to external sources. The stability of these solutions is analyzed by counting the number of preserved supersymmetries. It is shown that static massive (D-3)-branes are unstable unless some suitable gauge fields are added and the brane is extremal. In particular, in three dimensions, a 0-brane is recognized as the negative mass counterpart of the BTZ black hole. For these 0-branes, we write explicitly electromagnetically charged BPS states with various number of preserved supersymmetries within the OSp(p|2) x OSp(q|2) supergroups. In five dimensions, we prove that stable 2-branes with electromagnetic charge always exist for the generic supergroup SU(2,2|N), where N is different than 4. For the special case N=4, in which the CS supergravity requires the addition of a nontrivial gauge field configuration in order to preserve maximal number of degrees of freedom, we show for two different static 2-branes that they are BPS states (one of which is the ground state), and from the corresponding algebra of charges we show that the energy is bounded from below. In higher dimensions, our results admit a straightforward generalization, although there are presumably more solutions corresponding to different intersections of the elementary objects.Comment: 43 pages, revtex4.cls; v2: slight amendments and references added to match published versio

Preparing Youth for College and Career: A Process Evaluation of Urban Alliance

Urban Alliance, headquartered in Washington, DC, serves at-risk youth through its high school internship program, which provides training, mentoring, and work experience to high school seniors from distressed communities in Washington, DC; Baltimore; Northern Virginia; and Chicago. The program serves youth before they become disconnected, helping them successfully transition to higher education or employment after graduation. Urban Alliance has commissioned the Urban Institute to conduct a six-year, randomized controlled trial impact and process evaluation of its high school internship program. This report provides a process analysis of the program; the analysis is informed by extensive evaluator observation and interviews with staff, stakeholders, and youth. It also presents baseline information about Urban Alliance and the youth participating in its high school internship program in Washington, DC, and Baltimore in the 2011–12 and 2012–13 program years. Subsequent reports as part of the impact study will describe the early-adulthood impacts of the Urban Alliance internship program on the youth it serves. Below is a summary of the findings in this first of three reports

Wrapped branes with fluxes in 8d gauged supergravity

We study the gravity dual of several wrapped D-brane configurations in presence of 4-form RR fluxes partially piercing the unwrapped directions. We present a systematic approach to obtain these solutions from those without fluxes. We use D=8 gauged supergravity as a starting point to build up these solutions. The configurations include (smeared) M2-branes at the tip of a G_2 cone on S^3 x S^3, D2-D6 branes with the latter wrapping a special Lagrangian 3-cycle of the complex deformed conifold and an holomorphic sphere in its cotangent bundle T^*S^2, D3-branes at the tip of the generalized resolved conifold, and others obtained by means of T duality and KK reduction. We elaborate on the corresponding N=1 and N=2 field theories in 2+1 dimensions.Comment: 32 pages, LateX, v2: minor changes, reference added, v3: section 3.5.2 improve

Prepotential and Instanton Corrections in N=2 Supersymmetric SU(N_1)xSU(N_2) Yang Mills Theories

In this paper we analyse the non-hyperelliptic Seiberg-Witten curves derived from M-theory that encode the low energy solution of N=2 supersymmetric theories with product gauge groups. We consider the case of a SU(N_1)xSU(N_2) gauge theory with a hypermultiplet in the bifundamental representation together with matter in the fundamental representations of SU(N_1) and SU(N_2). By means of the Riemann bilinear relations that hold on the Riemann surface defined by the Seiberg--Witten curve, we compute the logarithmic derivative of the prepotential with respect to the quantum scales of both gauge groups. As an application we develop a method to compute recursively the instanton corrections to the prepotential in a straightforward way. We present explicit formulas for up to third order on both quantum scales. Furthermore, we extend those results to SU(N) gauge theories with a matter hypermultiplet in the symmetric and antisymmetric representation. We also present some non-trivial checks of our results.Comment: 21 pages, 2 figures, minor changes and references adde

Let's Twist Again: General Metrics of G(2) Holonomy from Gauged Supergravity

We construct all complete metrics of cohomogeneity one G(2) holonomy with S^3 x S^3 principal orbits from gauged supergravity. Our approach rests on a generalization of the twisting procedure used in this framework. It corresponds to a non-trivial embedding of the special Lagrangian three-cycle wrapped by the D6-branes in the lower dimensional supergravity. There are constraints that neatly reduce the general ansatz to a six functions one. Within this approach, the Hitchin system and the flop transformation are nicely realized in eight dimensional gauged supergravity.Comment: 31 pages, latex; v2: minor changes, references adde

Self-dual solitons in N=2 supersymmetric semilocal Chern-Simons theory

We embed the semilocal Chern-Simons-Higgs theory into an N=2 supersymmetric system. We construct the corresponding conserved supercharges and derive the Bogomol'nyi equations of the model from supersymmetry considerations. We show that these equations hold provided certain conditions on the coupling constants as well as on the Higgs potential of the system, which are a consequence of the huge symmetry of the theory, are satisfied. They admit string-like solutions which break one half of the supersymmetries --BPS Chern-Simons semilocal cosmic strings-- whose magnetic flux is concentrated at the center of the vortex. We study such solutions and show that their stability is provided by supersymmetry through the existence of a lower bound for the energy, even though the manifold of the Higgs vacuum does not contain non-contractible loops.Comment: 12 pages, LaTeX, no figures, to appear in Modern Physics Letters

Supersymmetric Electroweak Cosmic Strings

We study the connection between $N=2$ supersymmetry and a topological bound in a two-Higgs-doublet system with an $SU(2)\times U(1)_Y\times U(1)_{Y^{\prime}}$ gauge group. We derive the Bogomol'nyi equations from supersymmetry considerations showing that they hold provided certain conditions on the coupling constants, which are a consequence of the huge symmetry of the theory, are satisfied. Their solutions, which can be interpreted as electroweak cosmic strings breaking one half of the supersymmetries of the theory, are studied. Certain interesting limiting cases of our model which have recently been considered in the literature are finally analyzed.Comment: 20 pages, RevTe

Helical vortex phase in the non-centrosymmetric CePt_3Si

We consider the role of magnetic fields on the broken inversion superconductor CePt_3Si. We show that upper critical field for a field along the c-axis exhibits a much weaker paramagnetic effect than for a field applied perpendicular to the c-axis. The in-plane paramagnetic effect is strongly reduced by the appearance of helical structure in the order parameter. We find that to get good agreement between theory and recent experimental measurements of H_{c2}, this helical structure is required. We propose a Josephson junction experiment that can be used to detect this helical order. In particular, we predict that Josephson current will exhibit a magnetic interference pattern for a magnetic field applied perpendicular to the junction normal. We also discuss unusual magnetic effects associated with the helical order.Comment: 5 pages, 2 figures, Accepted as Phys Rev. Lette

Gauge/String Duality in Confining Theories

This is the content of a set of lectures given at the XIII Jorge Andre Swieca Summer School on Particles and Fields, held in Campos do Jordao, Brazil in January 2005. They intend to be a basic introduction to the topic of gauge/gravity duality in confining theories. We start by reviewing some key aspects of the low energy physics of non-Abelian gauge theories. Then, we present the basics of the AdS/CFT correspondence and its extension both to gauge theories in different spacetime dimensions with sixteen supercharges and to more realistic situations with less supersymmetry. We discuss the different options of interest: placing D-branes at singularities and wrapping D-branes in calibrated cycles of special holonomy manifolds. We finally present an outline of a number of non-perturbative phenomena in non-Abelian gauge theories as seen from supergravity.Comment: 70 pages, 8 figures, Lectures given at XIII Jorge Andre Swieca Summer School on Particle and Fields, Campos do Jordao, Brazil, January 2005; v2: several explanations were expanded and improved while an oversight, some typos and the list of references were corrected; v3: minor amendments and a few references added; v4: citations added, final versio