Nodular anhydrite growth controlled by pedogenic structures in evaporite lake formations

Several nodular gypsum beds exhibiting a remarkable vertical arrangement of individual nodules are present in the Miocene continental evaporite formations of the Calatayud Basin, northeastern Spain. The growth of the gypsum nodules, initially anhydrite, took place within magnesitic carbonate deposits which display incipient pedogenic features such as rhizoliths and clotted to peloidal textures. Simultaneous and after the pedogenic modification of the carbonate substratum, displacing nodules started to grow, their arrangement being closely conditioned by the development of vertical fissuring related to root penetration. The transformation of anhydrite to gypsum was probably realized early after little burial of the sulphate–carbonate deposits. The occurrence of vertically oriented gypsum nodules can be seen as a diagnostic feature for palustrine conditions developed in evaporitic lake settings, this peculiar morphology of the sulphate nodules having been strongly controlled by the internal structure of the palustrine palaeosols

Heavy Quarkonium States with the Holographic Potential

The quarkonium states in a quark-gluon plasma is examined with the heavy quark potential implied by the holographic principle. Both the vanila AdS-Schwarzschild metric and the one with an infrared cutoff are considered. The dissociation temperature is calculated by solving the Schr\"o dinger equation of the potential model. In the case of the AdS-Schwarzschild metric with a IR cutoff, the dissociation temperatures for $J/\psi$ and $\Upsilon$ with the U-ansatz of the potential are found to agree with the lattice results within a factor of two.Comment: 9 pages with 2 figues in Revte

AdS/CFT, Multitrace Deformations and New Instabilities of Nonlocal String Theories

We study "multitrace" deformations of large N master fields in models with a mass gap. In particular, we determine the conditions for the multitrace couplings to drive tachyonic instabilities. These tachyons represent new local instabilities of the associated nonlocal string theories. In the particular case of Dp-branes at finite temperature, we consider topology-changing phase transitions and the effect of multitrace perturbations on the corresponding phase diagrams.Comment: harvmac. 28 pages. 9 eps figure

Strongly bound mesons at finite temperature and in magnetic fields from AdS/CFT

We study mesons in N=4 super Yang-Mills theory with fundamental flavors added at large 't Hooft coupling using the gauge/gravity correspondence. High-spin mesons are well described by using semiclassical string configurations. We determine the meson spectrum at finite temperature and in a background magnetic field.Comment: 15 pages, 11 figures; v2: references adde

Holographic Meson Melting

The plasma phase at high temperatures of a strongly coupled gauge theory can be holographically modelled by an AdS black hole. Matter in the fundamental representation and in the quenched approximation is introduced through embedding D7-branes in the AdS-Schwarzschild background. Low spin mesons correspond to the fluctuations of the D7-brane world volume. As is well known by now, there are two different kinds of embeddings, either reaching down to the black hole horizon or staying outside of it. In the latter case the fluctuations of the D7-brane world volume represent stable low spin mesons. In the plasma phase we do not expect mesons to be stable but to melt at sufficiently high temperature. We model the late stages of this meson melting by the quasinormal modes of D7-brane fluctuations for the embeddings that do reach down to the horizon. The inverse of the imaginary part of the quasinormal frequency gives the typical relaxation time back to equilibrium of the meson perturbation in the hot plasma. We briefly comment on the possible application of our model to quarkonium suppression.Comment: 25+1 pages, 6 figures; v4: references adde

Energía gastada en el primer ciclo de histéresis como parámetro de selección de un biomaterial

Veinticuatro muestras de pericardio de ternera estabilizado, material similar al utilizado en la fabricación de velos de bioprótesis cardiacas, fueron sometidas a una prueba de esfuerzo a fatiga. Tras seis bloques de 100 ciclos a 1 MPa de presión máxima se rompieron 12 muestras, el 50%. La energía media gastada en este primer ciclo, en las muestras que sobrevivieron, fue de 0.16J, un valor inferior a la energía gastada en las muestra que terminaron rompiendo, 0.28J (p=0.005). Utilizando el cociente entre la energía disipada en el primer ciclo y el espesor medio de la muestra, con un valor de corte de 0.48J/mm para la selección de las mejores muestras, se obtiene un índice de validez del 87.5%, y un área bajo la curva ROC de 0.917. Este método no destructivo debe ayudar a los métodos ópticos en el reconocimiento y selección de las muestras más resistentes y en la obtención del material biológico más homogéne

The Stress-Energy Tensor of Flavor Fields from AdS/CFT

We use the AdS/CFT correspondence to study the transport properties of massive N=2 hypermultiplet fields in an N=4 SU(Nc) super-Yang-Mills theory plasma in the large Nc, large 't Hooft coupling limit, and in the presence of a baryon number chemical potential and external electric and magnetic fields. In particular, we compute the flavor fields' contribution to the stress-energy tensor. We find infrared divergences in the stress-energy tensor, arising from the flavor fields' constant rate of energy and momentum loss. We regulate these divergences and extract the energy and momentum loss rates from the divergent terms. We also check our result in various limits in which the divergences are absent. The supergravity dual is a system of D7-branes, with a particular configuration of worldvolume fields, probing an AdS-Schwarzschild background. The supergravity calculation amounts to computing the stress-energy tensor of the D7-branes.Comment: 32 pages; v2, added one footnote in section 2.2, added one reference, version published in JHE

Critical Exponents from AdS/CFT with Flavor

We use the AdS/CFT correspondence to study the thermodynamics of massive N=2 supersymmetric hypermultiplet flavor fields coupled to N=4 supersymmetric SU(Nc) Yang-Mills theory, formulated on curved four-manifolds, in the limits of large Nc and large 't Hooft coupling. The gravitational duals are probe D-branes in global thermal AdS. These D-branes may undergo a topology-changing transition in the bulk. The D-brane embeddings near the point of the topology change exhibit a scaling symmetry. The associated scaling exponents can be either real- or complex-valued. Which regime applies depends on the dimensionality of a collapsing submanifold in the critical embedding. When the scaling exponents are complex-valued, a first-order transition associated with the flavor fields appears in the dual field theory. Real scaling exponents are expected to be associated with a continuous transition in the dual field theory. For one example with real exponents, the D7-brane, we study the transition in detail. We find two field theory observables that diverge at the critical point, and we compute the associated critical exponents. We also present analytic and numerical evidence that the transition expresses itself in the meson spectrum as a non-analyticity at the critical point. We argue that the transition we study is a true phase transition only when the 't Hooft coupling is strictly infinite.Comment: 31 pages, 21 eps files in 12 figures; v2 added one reference and one footnote, version published in JHE

Hot Defect Superconformal Field Theory in an External Magnetic Field

In this paper we investigate the influence of an external magnetic field on a flavoured holographic gauge theory dual to the D3/D5 intersection at finite temperature. Our study shows that the external magnetic field has a freezing effect on the confinement/ deconfinement phase transition. We construct the corresponding phase diagram. We investigate some thermodynamic quantities of the theory. A study of the entropy reveals enhanced relative jump of the entropy at the "chiral" phase transition. A study of the magnetization shows that both the confined and deconfined phases exhibit diamagnetic response. The diamagnetic response in the deconfined phase has a stronger temperature dependence reflecting the temperature dependence of the conductivity. We study the meson spectrum of the theory and analyze the stability of the different phases looking at both normal and quasi-normal semi-classical excitations. For the symmetry breaking phase we analyze the corresponding pseudo-Goldstone modes and prove that they satisfy non-relativistic dispersion relation.Comment: 42 pages, 14 figure

Black-hole quasinormal modes and scalar glueballs in a finite-temperature AdS/QCD model

We use the holographic AdS/QCD soft-wall model to investigate the spectrum of scalar glueballs in a finite temperature plasma. In this model, glueballs are described by a massless scalar field in an AdS_5 black hole with a dilaton soft-wall background. Using AdS/CFT prescriptions, we compute the boundary retarded Green's function. The corresponding thermal spectral function shows quasiparticle peaks at low temperatures. We also compute the quasinormal modes of the scalar field in the soft-wall black hole geometry. The temperature and momentum dependences of these modes are analyzed. The positions and widths of the peaks of the spectral function are related to the frequencies of the quasinormal modes. Our numerical results are found employing the power series method and the computation of Breit-Wigner resonances.Comment: Revision: Results unchanged. More discussions on the model and on the results. References added. 28 pages, 7 figures, 5 table