One-loop effects from spin-1 resonances in Composite Higgs models

We compute the 1-loop correction to the electroweak observables from spin-1 resonances in SO(5)/SO(4) composite Higgs models. The strong dynamics is modeled with an effective description comprising the Nambu-Goldstone bosons and the lowest-lying spin-1 resonances. A classification is performed of the relevant operators including custodially-breaking effects from the gauging of hypercharge. The 1-loop contribution of the resonances is extracted in a diagrammatic approach by matching to the low-energy theory of Nambu-Goldstone bosons. We find that the correction is numerically important in a significant fraction of the parameter space and tends to weaken the bounds providing a negative shift to the S parameter.Comment: 45 pages, 13 figures. v2: minor corrections, conclusions unchanged. v3: two diagrams in Fig.13 correctly redraw

Dispersion Relations for Electroweak Observables in Composite Higgs Models

We derive dispersion relations for the electroweak oblique observables measured at LEP in the context of $SO(5)/SO(4)$ composite Higgs models. It is shown how these relations can be used and must be modified when modeling the spectral functions through a low-energy effective description of the strong dynamics. The dispersion relation for the parameter $\epsilon_3$ is then used to estimate the contribution from spin-1 resonances at the 1-loop level. Finally, it is shown that the sign of the contribution to the $\hat S$ parameter from the lowest-lying spin-1 states is not necessarily positive definite, but depends on the energy scale at which the asymptotic behavior of current correlators is attained.Comment: 34 pages, 4 figures. v2: a few minor changes, typos corrected, list of references revise

The electrochemical stability of thiols on gold surfaces

In this paper we present a comparative analysis of the electrochemical stability of alkanethiols, aromatic and heterocyclic thiols on the Au(111) and Au(100) faces in relation to the theoretical energetic data. The peak potential and surface coverage are used as the key parameters to estimate the electrochemical stability while work function changes, adsorption energies and surface free energies calculated from periodic DFT, including van der Waals interactions, are used for the theoretical estimation. We find that the peak potentials do not correlate with work function changes and adsorption energies in particular for aromatic and heterocyclic thiols. In contrast, the reductive desorption potentials for the different thiols show a good correlation with the surface free energy of the SAMs estimated by density functional theory calculations. Surface coverage is a key factor that controls reductive desorption through van der Waals interactions.Fil: Salvarezza, Roberto Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Carro, Pilar. Universidad de La Laguna; Españ

Dynamics of Rough Interfaces in Chemical Vapor Deposition: Experiments and a Model for Silica Films

We study the surface dynamics of silica films grown by low pressure chemical vapor deposition. Atomic force microscopy measurements show that the surface reaches a scale invariant stationary state compatible with the Kardar-Parisi-Zhang (KPZ) equation in three dimensions. At intermediate times the surface undergoes an unstable transient due to shadowing effects. By varying growth conditions and using spectroscopic techniques, we determine the physical origin of KPZ scaling to be a low value of the surface sticking probability, related to the surface concentration of reactive groups. We propose a stochastic equation that describes the qualitative behavior of our experimental system.Comment: 5 two-column pages, Revtex, 5 figures, to appear in Phys. Rev. Let

Complex processes related to the early stages of mercury electrodeposition on Pt electrodes

The underpotential deposition and early stages of bulk mercury electrodeposition on platinum from aqueous solution containing Hg2+2 ions were studied by using combined potentiostatic and potentiodynamic techniques. The simultaneous electroreduction of the O-containing surface species and the underpotential deposition of Hgsup>2+2 ions render an electrode surface containing an O/Hg atom ratio which depends on both the applied potential and Hgsup>2+2 ion concentration in solution. The nucleation and growth of bulk mercury is impeded by the presence of O-containing surface species, whereas it is markedly enhanced by the presence of Hg-adatoms on the electrode surface. A small number of sites are involved in the nucleation process. Apparently defective points at the UPD Hg layer act as preferred sites for nucleation. It takes potentials more negative than the reversible potential of the Hg/Hgsup>2+2 ion electrode and relatively long electrodeposition times to achieve a degree of surface coverage by mercury atoms greater than 1. It is possible to observe that a fraction of them penetrates into bulk platinum to form a skin-type Hg-Pt alloy.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

From regular to irregular solid electrode surfaces : A systematic approach to their characterization

A description of solid surfaces of interest for electrochemical reactions which is based on the analysis of scanning tunneling microscopy images is presented. Real single-crystal surfaces are better described as weakly disordered surfaces, in contrast to strongly disordered surfaces. Under certain conditions both anisotropic and isotropic strongly disordered surfaces exhibit fractal properties. The rationale of rough surfaces can be attempted by applying the dynamic scaling theory to analyze STM profiles. Examples from regular to irregular solid surfaces are given covering from real single-crystal and faceted metals to columnar structured and branched metal surfaces. Roughness caused by adsorbates and electropolymer coatings are also considered.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Progress in the knowledge of irregular solid electrode surfaces

Modern approaches to solid surface disorder provide a more rigourous way of defining roughness at solid surfaces, a crucial concept in electrocatalysis. The study of this type of surface comprises growth kinetics, geometric description, relaxation kinetics and influence of surface irregularities on different reactions. Continuous rough columnar structured metal surfaces constitute a good model system for the investigation of a number of processes which are of special interest in heterogeneous catalysis, including electrocatalysis. The topography of these metal surfaces can be determined by scanning tunneling microscopy (STM) at different scales and can be described by means of the dynamic scaling theory applied to STM imaging. Roughness relaxation kinetics followed by electrochemical techniques can be interpreted through a coalescence-type mechanism. Typical examples of adsorption and diffusion controlled electrochemical reactions on this type of electrodes are presented.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Spatial distribution of pits on stainless steel

The spatial distribution of pits formed on a stainless steel electrode is analysed by means of two stochastic criteria based on the Poisson distribution law. Information is obtained about the character of the location of pits on the electrode surface.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Thermal Stability of Self-Assembled Monolayers of n-Hexanethiol on Au(111)-(1 × 1) and Au(001)-(1 × 1)

Thermal desorption in an ultrahigh vacuum of n-hexanethiol (C6T) self-assembled monolayers (SAMs) prepared from ethanolic solutions on Au(111) and Au(001) unreconstructed surfaces was investigated by X-ray photoelectron spectroscopy. The SAMs desorption was performed from room temperature (RT) to 380 K. We report that the hexanethiolate surface saturation coverage is bigger (∼0.4 ML) for the SAM on Au(001) than on Au(111) (∼0.33 ML). We identified a greater stability for C6T SAMs on Au(001). Large amounts of physisorbed species were found on preferred oriented (111) polycrystalline Au at the low coverage regime at RT, while the SAM on the Au(001) single crystal at this conditions desorbs at a steady pace. At 340 K, both SAMs remain stable at the coverage expected for the lying-down phases that maximizes the van der Waals interactions. We observe that at higher temperatures the carbon alpha-sulfur bond breaks, producing free S on both gold surfaces.Fil: Cristina, Lucila Josefina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Ruano Sandoval, Gustavo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; ArgentinaFil: Salvarezza, Roberto Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas; ArgentinaFil: Ferron, Julio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Física del Litoral. Universidad Nacional del Litoral. Instituto de Física del Litoral; Argentina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Departamento de Materiales; Argentin

Validity of the linear growth equation for interface evolution for copper electrodeposition in the presence of organic additives

The interface evolution of copper electrodeposits produced on copper from a thiorea-derivative-containing acid plating bath at a low current density and 298 K was studied by atomic force microscopy (AFM). The dynamic scaling theory was applied to AFM images leading to scaling exponents, which are consistent with the predictions of the complete linear equation for interface growth. In agreement with the theory, experimental data show, for the interface evolution, a crossover from a surface diffusion controlled regime to an Edwards-Wilkinson regime as the length scale increases.Instituto de Investigaciones Fisicoquímicas Teóricas y AplicadasFacultad de Ciencias Exacta