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Bergshoeff E.A.,University of Groningen | Ortin T.,Institute Fisica Teorica UAM CSIC | Riccioni F.,University of Rome La Sapienza
Nuclear Physics B | Year: 2012

We discuss some general properties of "defect branes", i.e. branes of co-dimension two, in (toroidally compactified) IIA/IIB string theory. In particular, we give a full classification of the supersymmetric defect branes in dimensions 3 ≤ D≤ 10 as well as their higher-dimensional string and M-theory origin as branes and a set of "generalized" Kaluza-Klein monopoles. We point out a relation between the generalized Kaluza-Klein monopole solutions and a particular type of mixed-symmetry tensors. These mixed-symmetry tensors can be defined at the linearized level as duals of the supergravity potentials that describe propagating degrees of freedom. It is noted that the number of supersymmetric defect branes is always twice the number of corresponding central charges in the supersymmetry algebra. © 2011 Elsevier B.V. Source


Rolbiecki K.,Institute Fisica Teorica UAM CSIC | Tattersall J.,University of Heidelberg
Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics | Year: 2015

If light supersymmetric top (stop) quarks are produced at the LHC and decay via on- or off-shell W-bosons they can be expected to contribute to a precision W+W- cross section measurement. Using the latest results of the CMS experiment, we revisit constraints on the stop quark production and find that this measurement can exclude portions of the parameter space not probed by dedicated searches. In particular we can exclude light top squarks up to 230 GeV along the line separating three- and four-body decays, t~1→χ~10W(*)b. We also study the exclusion limits in case when the branching ratio for these decays is reduced and show significant improvement over previously existing limits. © 2015 The Authors. Source


Bueno P.,Institute Fisica Teorica UAM CSIC | Myers R.C.,Perimeter Institute for Theoretical Physics | Witczak-Krempa W.,Perimeter Institute for Theoretical Physics
Physical Review Letters | Year: 2015

We study the contribution to the entanglement entropy of (2+1)-dimensional conformal field theories (CFTs) coming from a sharp corner in the entangling surface. This contribution is encoded in a function a(θ) of the corner opening angle, and was recently proposed as a measure of the degrees of freedom in the underlying CFT. We show that the ratio a(θ)/CT, where CT is the central charge in the stress tensor correlator, is an almost universal quantity for a broad class of theories including various higher-curvature holographic models, free scalars, and fermions, and Wilson-Fisher fixed points of the O(N) models with N=1,2,3. Strikingly, the agreement between these different theories becomes exact in the limit θ→π, where the entangling surface approaches a smooth curve. We thus conjecture that the corresponding ratio is universal for general CFTs in three dimensions. © 2015 American Physical Society. © 2015 American Physical Society. Source


Bueno P.,Institute Fisica Teorica UAM CSIC | Myers R.C.,Perimeter Institute for Theoretical Physics
Journal of High Energy Physics | Year: 2015

Abstract: The entanglement entropy of three-dimensional conformal field theories contains a universal contribution coming from corners in the entangling surface. We study these contributions in a holographic framework and, in particular, we consider the effects of higher curvature interactions in the bulk gravity theory. We find that for all of our holographic models, the corner contribution is only modified by an overall factor but the functional dependence on the opening angle is not modified by the new gravitational interactions. We also compare the dependence of the corner term on the new gravitational couplings to that for a number of other physical quantities, and we show that the ratio of the corner contribution over the central charge appearing in the two-point function of the stress tensor is a universal function for all of the holographic theories studied here. Comparing this holographic result to the analogous functions for free CFT’s, we find fairly good agreement across the full range of the opening angle. However, there is a precise match in the limit where the entangling surface becomes smooth, i.e., the angle approaches π, and we conjecture the corresponding ratio is a universal constant for all three-dimensional conformal field theories. In this paper, we expand on the holographic calculations in our previous letter arXiv:1505.04804, where this conjecture was first introduced. © 2015, The Author(s). Source


Iocco F.,Institute Fisica Teorica UAM CSIC | Pato M.,Sao Paulo State University | Bertone G.,TU Munich | Bertone G.,The Oskar Klein Center | Bertone G.,University of Amsterdam
Nature Physics | Year: 2015

The ubiquitous presence of dark matter in the Universe is today a central tenet in modern cosmology and astrophysics. Throughout the Universe, the evidence for dark matter is compelling in dwarfs, spiral galaxies, galaxy clusters as well as at cosmological scales. However, it has been historically difficult to pin down the dark matter contribution to the total mass density in the Milky Way, particularly in the innermost regions of the Galaxy and in the solar neighbourhood. Here we present an up-to-date compilation of Milky Way rotation curve measurements, and compare it with state-of-the-art baryonic mass distribution models. We show that current data strongly disfavour baryons as the sole contribution to the Galactic mass budget, even inside the solar circle. Our findings demonstrate the existence of dark matter in the inner Galaxy without making any assumptions about its distribution. We anticipate that this result will compel new model-independent constraints on the dark matter local density and profile, thus reducing uncertainties on direct and indirect dark matter searches, and will help reveal the structure and evolution of the Galaxy. Source

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