678 research outputs found
Constraints on Regge models from perturbation theory
We study the constraints that the operator product expansion imposes on large
inspired QCD models for current-current correlators. We focus on the
constraints obtained by going beyond the leading-order parton computation. We
explicitly show that, assumed a given mass spectrum: linear Regge behavior in
(the principal quantum number) plus corrections in , we can obtain the
logarithmic (and constant) behavior in of the decay constants within a
systematic expansion in . Our example shows that it is possible to have
different large behavior for the vector and pseudo-vector mass spectrum and
yet comply with all the constraints from the operator product expansion.Comment: 14 pages, 6 figures; two references added, numerical analysis
extended, main conclusions unchange
On the relevance of large scale pulsed-laser deposition: Evidence of structural heterogeneities in ZnO thin films
Pulsed-laser deposition is known as a well-suited method for growing thin films of oxide compounds presenting a wide range of functional properties. A limitation of this method for industrial process is the very anisotropic expansion dynamics of the plasma plume, which induces difficulties to grow on large scale films with homogeneous thickness and composition. The specific aspect of the crystalline or orientation uniformity has not been investigated, despite its important role on oxide films properties. In this work, the crystalline parameters and the texture of zinc oxide films are studied as a function of position with respect to the central axis of the plasma plume. We demonstrate the existence of large non-uniformities in the films. The stoichiometry, the lattice parameter, and the distribution of crystallites orientations drastically depend on the position with respect to the plume axis, i.e., on the oblique incidence of the ablated species. The origin of these non-uniformities, in particular, the unexpected tilted orientation of the ZnO c-axis may be attributed to the combined effects of the oblique incidence and of the ratio between oxygen and zinc fluxes reaching the surface of the growing film
Holographic U(1)_A and String Creation
We analyze the resolution of the U(1)_A problem in the Sakai-Sugimoto
holographic dual of large N_c QCD at finite temperature. It has been shown that
in the confining phase the axial symmetry is broken at order 1/N_c, in
agreement with the ideas of Witten and Veneziano. We show that in the
deconfined phase the axial symmetry remains unbroken to all orders in 1/N_c. In
this case the breaking is due to instantons which are described by spacelike
D0-branes, in agreement with 'tHooft's resolution. The holographic dual of the
symmetry breaking fermion condensate is a state of spacelike strings between
the D0-brane and the flavor D8-branes, which result from a spacelike version of
the string creation effect. In the intermediate phase of deconfinement with
broken chiral symmetry the instanton gas approximation is possibly regulated in
the IR, which would imply an eta' mass-squared of order exp(-N_c).Comment: 18 pages, 19 figures, minor change
Elaborations on the String Dual to N=1 SQCD
In this paper we make further refinements to the duality proposed between N=1
SQCD and certain string (supergravity plus branes) backgrounds, working in the
regime of comparable large number of colors and flavors. Using the string
theory solutions, we predict different field theory observables and phenomena
like Seiberg duality, gauge coupling and its running, the behavior of Wilson
and 't Hooft loops, anomalous dimensions of the quark superfields, quartic
superpotential coupling and its running, continuous and discrete anomaly
matching. We also give evidence for the smooth interpolation between higgsed
and confining vacua. We provide several matchings between field theory and
string theory computations.Comment: 44 pages, 6 figures. References added, minor rewritings, published
versio
Supporting clinical information management by NFC technology
Tele-monitorization is a problem with aging people living alone since the vital signs control is complicated for them. In this sense, some initiatives by adapting technologies make easy these controls. In this work we present a solution consist of the Near Field Communications technology adaptability. Mobile phones NFC enabled serving as a middleware between measure devices and people. In addition, a proposal for managing clinical information and medicine prescription are presented.Tele-monitorization is a problem with aging people living alone since the vital signs control is complicated for them. In this sense, some initiatives by adapting technologies make easy these controls. In this work we present a solution consist of the Near Field Communications technology adaptability. Mobile phones NFC enabled serving as a middleware between measure devices and people. In addition, a proposal for managing clinical information and medicine prescription are presented
Holographic duals of SQCD models in low dimensions
We obtain gravity duals to supersymmetric gauge theories in two and three
spacetime dimensions with unquenched flavor. The supergravity solutions are
generated by a set of color branes wrapping a compact cycle in a Calabi-Yau
threefold, together with another set of flavor branes extended along the
directions orthogonal to the cycle wrapped by the color branes. We construct
supergravity backgrounds which include the backreaction induced by a smeared
set of flavor branes, which act as delocalized dynamical sources of the
different supergravity fields.Comment: 42 pages, 5 figures;v2: typos correcte
The Structure of the Non-SUSY Baryonic Branch of Klebanov-Strassler
We study the two-dimensional space of supergravity solutions corresponding to
non-supersymmetric deformations of the baryonic branch of Klebanov-Strassler.
By combining analytical methods with a numerical survey of the parameter space,
we find that this solution space includes as limits the softly-broken N=1
solutions of Gubser et al. and those of Dymarsky and Kuperstein. We also
identify a one-dimensional family of solutions corresponding to a natural
non-supersymmetric generalisation of Klebanov-Strassler, and one corresponding
to the limit in which supersymmetry is completely absent, even in the far UV.
For almost all of the parameter space we find indications that much of the
structure of the supersymmetric baryonic branch survives.Comment: 29 pages plus appendices, 11 figure
Aggressiveness of Fusarium oxysporum and F. verticillioides isolates on stone and scots pine under greenhouse conditions
Producción CientíficaScots pine (Pinus sylvestris) and Stone pine (Pinus pinea) are two important species used in re-forestation that are subject to damage by damping-off fungi in forest nurs-eries. Twenty-two isolates of Fusarium oxysporum and F. verticillioides from diseased seedlings of eight different hosts were tested for aggressiveness on seeds and seed-lings of both pine species, including the effects on seedling emergence and mortal-ity. Scots pine was more susceptible to damping-off than Stone pine, as indicated both by reduced seedling emergence and elevated seedling mortality. The impact of F. oxysporum and F. verticillioides on seeds and seedlings did not differ significantly for either pine species. Our findings support previous studies that found that these are damping-off pathogens on the studied pines. Whereas most isolates proved to be pathogenic, some isolates of both Fusarium species showed to be non- pathogenic.Ministerio de Ciencia e Innovación projects (PID2019-110459RB-I00) and (PLEC2021-008076
A Nexafs Study of Nitric Oxide Layers Adsorbed from a nitrite Solution onto a Pt(111) Surface
NO molecules adsorbed on a Pt(111) surface from dipping in an acidic nitrite
solution are studied by near edge X-ray absorption fine structure spectroscopy
(NEXAFS), X-ray photoelectron spectroscopy (XPS), low energy electron
diffraction (LEED) and scanning tunnelling microscopy (STM) techniques. LEED
patterns and STM images show that no long range ordered structures are formed
after NO adsorption on a Pt(111) surface. Although the total NO coverage is
very low, spectroscopic features in N K-edge and O K-edge absorption spectra
have been singled out and related to the different species induced by this
preparation method. From these measurements it is concluded that the NO
molecule is adsorbed trough the N atom in an upright conformation. The maximum
saturation coverage is about 0.3 monolayers, and although nitric oxide is the
major component, nitrite and nitrogen species are slightly co-adsorbed on the
surface. The results obtained from this study are compared with those
previously reported in the literature for NO adsorbed on Pt(111) under UHV
conditions
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