Hartree-Fock dynamics in highly excited quantum dots

Time-dependent Hartree-Fock theory is used to describe density oscillations of symmetry-unrestricted two-dimensional nanostructures. In the small amplitude limit the results reproduce those obtained within a perturbative approach such as the linearized time-dependent Hartree-Fock one. The nonlinear regime is explored by studying large amplitude oscillations in a non-parabolic potential, which are shown to introduce a strong coupling with internal degrees of freedom. This excitation of internal modes, mainly of monopole and quadrupole character, results in sizeable modifications of the dipole absorption.Comment: 4 pages, 4 embedded figure

Perceived effectiveness (vs Use) of coping (ACSQ) in soccer players

Este estudio analiza la estructura factorial de la versión española (Kim, Duda, Tomás y Balaguer, 2003) del Cuestionario de Aproximación al Afrontamiento en el Deporte (Approach to Coping in Sport Questionnaire, ACSQ-1, Kim, 1999; Kim y Duda, 1997) en 562 futbolistas. Adicionalmente, se plantea la validación de una versión adaptada del ACSQ diseñada para valorar la percepción de efectividad. Los resultados del CFA ponen de manifiesto un ajuste satisfactorio para ambos modelos ACSQ-uso y ACSQ-efectividad, observándose mejores indicadores para el modelo de efectividad (x2/gl=2.57; CFI= .913; TLI= .904; RMSEA= .058). Por otro lado, las relaciones de las diferentes dimensiones de afrontamiento en su versión uso y en su versión efectividad con las variables externas consideradas (ansiedad y autoconfianza) ponen de manifiesto el diferente papel de ambos criterios, y la necesidad, por lo tanto, de contemplar ambos indicadores en la valoración del coping en el ámbito deportivoThis study examines the factorial structure of the Spanish version (Kim, Duda, Tomás y Balaguer, 2003) of the Approach to Coping in Sport Questionnaire (ACSQ-1, Kim, 1999; Kim y Duda, 1997) in 562 soccer players. Additionally, a second aim of this study is to analyze the psychometric properties of an adapted version of ACSQ designed to assess perception of effectiveness. The results of CFA provided a satisfactory fit for both models ACSQ-use and ACSQ-effectiveness, showing better indexes for effectiveness model (x2/df = 2.57; CFI = .913; TLI = .904; RMSEA = .058). Moreover, the relations between ACSQ-use, ACSQ-effectiveness and the external variables (anxiety and self-confidence) show the different roles of both criteria, and the need, therefore, of contemplate both indicators in the assessment of coping in spor

Development of magnetic order in the TbNi(Al,In) series and magnetocrystalline anisotropy in TbTX compounds

9 páginas, 9 figuras, 4 tablas.-- PACS number(s): 71.20.Lp, 75.25.−j, 75.30.GwWe report on the magnetic structures in the TbNiAl1−xInx compounds as determined by powder neutron diffraction. These compounds belong to a large family of ternary rare-earth intermetallics crystallizing in the ZrNiAl-type hexagonal structure. All studied compounds order magnetically with magnetic structures characterized by k1=(0,0,0) and k2=(1/2,0,1/2) propagation vectors and magnetic moments aligned along or perpendicular to the hexagonal c axis. The magnetocrystalline anisotropy changes from uniaxial in the In-poor compounds (x≤0.4) to planar in the In-rich compounds (x≥0.5). The change of magnetocrystalline anisotropy type is a consequence of the development of structural parameters in the studied series. The Tb moments are oriented along the c axis when the nearest Tb-Tb distances between the planes are large compared to those within the planes, whereas Tb moments lie within the basal planes in the opposite case. This picture relating the structural parameters and anisotropy type can be generalized to the whole group of Tb-based compounds with the ZrNiAl type of structure.This work is a part of Research Project No. LG11024 financed by the Ministry of Education of the Czech Republic. The work was also supported by the Czech Science Foundation under Grant No. 202/09/1027. The work of M.K. was supported by Grant No. SVV-2011-263303.Peer reviewe

Band alignment at metal/ferroelectric interfaces: insights and artifacts from first principles

Based on recent advances in first-principles theory, we develop a general model of the band offset at metal/ferroelectric interfaces. We show that, depending on the polarization of the film, a pathological regime might occur where the metallic carriers populate the energy bands of the insulator, making it metallic. As the most common approximations of density functional theory are affected by a systematic underestimation of the fundamental band gap of insulators, this scenario is likely to be an artifact of the simulation. We provide a number of rigorous criteria, together with extensive practical examples, to systematically identify this problematic situation in the calculated electronic and structural properties of ferroelectric systems. We discuss our findings in the context of earlier literature studies, where the issues described in this work have often been overlooked. We also discuss formal analogies to the physics of polarity compensation at LaAlO3/SrTiO3 interfaces, and suggest promising avenues for future research.Comment: 29 pages, 23 figure

Signals of CP Violation Beyond the MSSM in Higgs and Flavor Physics

We study an extension of the Higgs sector of the Minimal Supersymmetric Standard Model (MSSM), considering the effects of new degrees of freedom at the TeV scale, and allowing for sources of CP violation beyond the MSSM (BMSSM). We analyze the impact of the BMSSM sources of CP violation on the Higgs collider phenomenology and on low energy flavor and CP violating observables. We identify distinct Higgs collider signatures that cannot be realized, either in the case without CP violating phases or in the CP violating MSSM, and investigate the prospects to probe them at the Tevatron and the LHC. The most striking benchmark scenario has three neutral Higgs bosons that all decay dominantly into W boson pairs and that are well within the reach of the 7 TeV LHC run. On the other hand, we also present scenarios with three Higgs bosons that have masses M_Hi > 150 GeV and decay dominantly into b bbar. Such scenarios are much more challenging to probe and can even lie completely outside the reach of the 7 TeV LHC run. We explore complementary scenarios with standard MSSM Higgs signals that allow to accommodate a sizable B_s mixing phase as indicated by D0, as well as the excess in B_s --> mu+ mu- candidates recently reported by CDF. We find that, in contrast to the MSSM, a minimal flavor violating soft sector is sufficient to generate significant corrections to CP violating observables in meson mixing, compatible with EDM constraints. In particular, a sizable B_s mixing phase, S_psiphi < 0.4, can be achieved for specific regions of parameter space. Such a large B_s mixing phase would unambiguously imply a sizable suppression of S_psiKs with respect to the SM prediction and a BR(B_s --> mu+ mu-) close to the 95% C.L. upper bound reported by CDF.Comment: 58 pages, 15 figures, 2 tables, v2 matches published versio

Two-dimensional electron gas at the PbTi O3/SrTi O3 interface: An ab initio study

In the polar catastrophe scenario, polar discontinuity accounts for the driving force of the formation of a two-dimensional electron gas (2DEG) at the interface between polar and nonpolar insulators. In this paper, we substitute the usual, nonferroelectric, polar material with a ferroelectric thin film and use the ferroelectric polarization as the source for polar discontinuity. We use ab initio simulations to systematically investigate the stability, formation, and properties of the two-dimensional free-carrier gases formed in PbTiO3/SrTiO3 heterostructures under realistic mechanical and electrical boundary conditions. Above a critical thickness, the ferroelectric layers can be stabilized in the out-of-plane monodomain configuration due to the electrostatic screening provided by the free carriers. Our simulations also predict that the system can be switched between three stable configurations (polarization up, down, or zero), allowing the nonvolatile manipulation of the free-charge density and sign at the interface. Furthermore, the link between ferroelectric polarization and free-charge density demonstrated by our analysis constitutes compelling support for the polar catastrophe model that is used to rationalize the formation of 2DEG at oxide interfaces

Macroscopic and microscopic study of a CePdIn compound

The magnetization and electrical resistivity measurements on a CePdIn single crystal as well as its preparation and structural characterization are presented. The negative paramagnetic Curie temperatures indicate antiferromagnetic ground state, the anisotropy of the paramagnetic Curie temperature amounts 22.7 K. No ferromagnetic correlations were indicated. Powder neutron diffraction experiment performed at temperatures down to 0.4 K did not lead to observation of any magnetic peak in diffraction patterns. We estimate the magnetic moment on Ce atoms to be significantly lower than 0.5-B. The temperature development of lattice parameters documents the standard thermal expansion of the unit cell; no signs of structural phase transition were observed

Artificially Disordered Birefringent Optical Fibers

We develop and experimentally verify a theory of evolution of polarization in artificially-disordered multi-mode optical fibers. Starting with a microscopic model of photo-induced index change, we obtain the first and second order statistics of the dielectric tensor in a Ge-doped fiber, where a volume disorder is intentionally inscribed via UV radiation transmitted through a diffuser. A hybrid coupled-power & coupled-mode theory is developed to describe the transient process of de-polarization of light launched into such a fiber. After certain characteristic distance, the power is predicted to be equally distributed over all co-propagating modes of the fiber regardless of their polarization. Polarization-resolved experiments, confirm the predicted evolution of the state of polarization. Complete mode mixing in a segment of fiber as short as ~ 10cm after 3.6dB insertion loss is experimentally observed. Equal excitation of all modes in such a multi-mode fiber creates the conditions to maximize the information capacity of the system under e.g. multiple-input-multiple-output (MIMO) transmission setup

Secuenciación dinámica de sistemas de fabricación flexible mediante aprendizaje automático: análisis de los principales sistemas de secuenciación existentes

Una forma habitual de secuenciar de modo dinámico los trabajos en los sistemas de fabricación es mediante el empleo de reglas de secuenciación. Sin embargo, el problema que presenta este método es que el comportamiento del sistema de fabricación dependerá de su estado, y no existe una regla que supere a las demás en todos los posibles estados que puede presentar el sistema de fabricación. Por lo tanto, sería interesante usar en cada momento la regla más adecuada. Para lograr este objetivo, se pueden utilizar sistemas de secuenciación que emplean aprendizaje automático que permiten, analizando el comportamiento previo del sistema de fabricación (ejemplos de entrenamiento), obtener el conocimiento necesario para determinar la regla de secuenciación más apropiada en cada instante. En el presente trabajo se realiza una revisión de los principales sistemas de secuenciación existentes en la literatura que utilizan aprendizaje automático para variar de forma dinámica la regla de secuenciación empleada en cada momento