162,049 research outputs found
Instantons on D7 brane probes and AdS/CFT with flavour
No full textRecent work on adding flavour to the generalized AdS/CFT correspondence is reviewed. In particular, we consider instanton configurations on two coincident D7 brane probes. These are matched to the Higgs branch of the dual field theory. In AdS5 × S5, the instanton generates a flow of the meson spectrum. For non-supersymmetric gravity backgrounds, the Higgs branch is lifted by a potential with non-trivial physical implications. Based on talk given by J. Erdmenger
Conditions on holographic entangling surfaces in higher curvature gravity
No full textWe study the extremal surfaces of functionals recently proposed for the holographic calculation of entanglement entropy in general higher curvature theories, using New Massive gravity and Gauss-Bonnet gravity as concrete examples. We show that the entropy functionals admit closed extremal surfaces, which for black hole backgrounds can encircle the event horizon of the black hole. In the examples considered, such closed surfaces correspond to a lower value of the entropy functional than expected from CFT calculations, implying a seeming mismatch between the bulk and boundary calculations. For Lorentzian settings we show that this problem can be resolved by imposing a causality constraint on the extremal surfaces. The possibility of deriving conditions from an alternative conical boundary condition method as proposed by Lewkowycz and Maldacena is explored
Heavy-light mesons from the AdS/CFT correspondence
No full textWe propose a holographic description of heavy-light mesons, i.e. of mesons containing a light and a heavy quark. In the semi-classical string limit, we look at the dynamics of strings tied between two D7 branes. We consider this setup both in an AdS background and in the non-supersymmetric Constable-Myers geometry which induces chiral symmetry breaking. We compute the meson masses in each case. Finally we discuss the results relevance for phenomenological comparison to the physical b-quark sector
SUPERCONDUCTING STATES FROM SPIN FLUCTUATION MECHANISMS
No full textSCHARNBERG K, Dahm T, ERDMENGER J. SUPERCONDUCTING STATES FROM SPIN FLUCTUATION MECHANISMS. Physica B Condensed Matter. 1994;194-196:1435-1436.The exchange of antiferromagnetic spin fluctuations leads to highly anisotropic pairing interactions with attractive as well as repulsive contributions. Using these pairing interactions, the order parameter DELTA (k over arrow pointing right, T) is calculated for different quasiparticle dispersion relations and band fillings. The effect of specific momentum dependences of the order parameter on the tunneling density of states and the size of the apparent gap is discussed
A gravity dual of chiral symmetry breaking
No full textWe establish a holographic description of chiral symmetry breaking for a particular confining large N non-supersymmetric gauge theory with matter in the fundamental representation. The gravity dual of this theory is obtained by introducing a D7-brane probe into a deformed Anti-de Sitter background found by Constable and Myers. We numerically compute the condensate and meson spectrum by solving the equation of motion of the D7-brane probe in this background. We find a symmetry breaking condensate as well as the associated, pion-like, Goldstone boson in the limit of small quark mass. The existence of the condensate ensures that the D7-brane never reaches the naked singularity at the origin of the deformed AdS space
Mesons in gauge/gravity duals: a review
No full textWe review recent progress in studying mesons within gauge/gravity duality, in the context of adding flavour degrees of freedom to generalizations of the AdS/CFT correspondence. Our main focus is on the "top-down approach" of considering models constructed within string theory. We explain the string-theoretical constructions in detail, aiming at non-specialists. These give rise to a new way of describing strongly coupled confining large-N gauge theories similar to large-N QCD. In particular, we consider gravity dual descriptions of spontaneous chiral symmetry breaking, and compare with lattice results. A further topic covered is the behaviour of flavour bound states in finite-temperature field theories dual to a gravity background involving a black hole. We also describe the "bottom up" phenomenological approach to mesons within AdS/QCD. Some previously unpublished results are also included.<br/
Chiral symmetry breaking and pions in nonsupersymmetric gauge/gravity duals
No full textWe study gravity duals of large N nonsupersymmetric gauge theories with matter in the fundamental representation by introducing a D7-brane probe into deformed AdS backgrounds. In particular, we consider a D7-brane probe in both the AdS Schwarzschild black hole solution and in the background found by Constable and Myers, which involves a nonconstant dilaton and S5 radius. Both these backgrounds exhibit confinement of fundamental matter and a discrete glueball and meson spectrum. We numerically compute the Psi-bar Psi condensate and meson spectrum associated with these backgrounds. In the AdS–black-hole background, a quark-bilinear condensate develops only at a nonzero quark mass. We speculate on the existence of a third order phase transition at a critical quark mass where the D7 embedding undergoes a geometric transition. In the Constable-Myers background, we find a chiral symmetry breaking condensate as well as the associated Goldstone boson in the limit of small quark mass. The existence of the condensate ensures that the D7-brane never reaches the naked singularity at the origin of the deformed AdS space. <br/
[Report to Chief J. E. Curry, by an unknown author #1]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
[Report to Chief J. E. Curry, by an unknown author #2]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
Quartic AdS interactions in higher-spin gravity from Conformal Field Theory
No full textClarifying the locality properties of higher-spin gravity is a pressing task, but notoriously difficult due to the absence of a weakly-coupled flat regime. The simplest non-trivial case where this question can be addressed is the quartic self-interaction of the AdS scalar field present in the higher-spin multiplet. We investigate this issue in the context of the holographic duality between the minimal bosonic higher-spin theory on AdS4 and the free O(N) vector model in three dimensions. In particular, we determine the exact explicit form of the derivative expansion of the bulk scalar quartic vertex. The quartic vertex is obtained from the field theory four-point function of the operator dual to the bulk scalar, by making use of our previous results for the Witten diagrams of higher-spin exchanges. This is facilitated by establishing the conformal block expansions of both the boundary four-point function and the dual bulk Witten diagram amplitudes. We show that the vertex we find satisfies a generalised notion of locality
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