Dependence of the vortex configuration on the geometry of mesoscopic flat samples

The influence of the geometry of a thin superconducting sample on the penetration of the magnetic field lines and the arrangement of vortices are investigated theoretically. We compare superconducting disks, squares and triangles with the same surface area having nonzero thickness. The coupled nonlinear Ginzburg-Landau equations are solved self-consistently and the important demagnetization effects are taken into account. We calculate and compare quantities like the free energy, the magnetization, the Cooper-pair density, the magnetic field distribution and the superconducting current density for the three geometries. For given vorticity the vortex lattice is different for the three geometries, i.e. it tries to adapt to the geometry of the sample. This also influences the stability range of the different vortex states. For certain magnetic field ranges we found a coexistence of a giant vortex placed in the center and single vortices toward the corners of the sample. Also the H-T phase diagram is obtained.Comment: 9 pages, 17 figures (submitted to Phys. Rev. B

Flux transitions in a superconducting ring

We perform a numeric study of the flux transitions in a superconducting ring at fixed temperature, while the applied field is swept at an ideally slow rate. The current around the ring and its free energy are evaluated. We partially explain some of the known experimental features, and predict a considerably large new feature: in the vicinity of a critical field, giant jumps are expected

Electron transport in a two-terminal Aharonov-Bohm ring with impurities

Electron transport in a two-terminal Aharonov-Bohm ring with a few short-range scatterers is investigated. An analytical expression for the conductance as a function of the electron Fermi energy and magnetic flux is obtained using the zero-range potential theory. The dependence of the conductance on positions of scatterers is studied. We have found that the conductance exhibits asymmetric Fano resonances at certain energies. The dependence of the Fano resonances on magnetic field and positions of impurities is investigated. It is found that collapse of the Fano resonances occurs and discrete energy levels in the continuous spectrum appear at certain conditions. An explicit form for the wave function corresponding to the discrete level is obtained.Comment: 25 pages (one-column), 8 figure

Faraday rotation in graphene

We study magneto--optical properties of monolayer graphene by means of quantum field theory methods in the framework of the Dirac model. We reveal a good agreement between the Dirac model and a recent experiment on giant Faraday rotation in cyclotron resonance. We also predict other regimes when the effects are well pronounced. The general dependence of the Faraday rotation and absorption on various parameters of samples is revealed both for suspended and epitaxial graphene.Comment: 10 pp; v2: typos corrected and references added, v3, v4: small changes and more reference

Sedentarismo, exercício físico e doenças crônicas

A inatividade física é fortemente relacionada à incidência e severidade de um vasto número de doenças crônicas. Assim sendo, o exercício físico torna-se uma das ferramentas terapêuticas mais importantes na promoção de saúde e o profissional de Educação Física, o responsável por sua ampla disseminação. Nesse artigo, discorremos sobre as seguintes questões: Qual o impacto - biológico e socioeconômico - da inatividade física na saúde dos indivíduos?; 2) Qual o impacto da inserção da atividade física vida dos indivíduos?; 3) Qual o papel da profissional de Educação Física na promoção de saúde e quais os desafios que a Educação Física, enquanto ciência ("lato sensu") e profissão, deve enfrentar nas próximas décadas? Tendo como ponto de partida o papel da inatividade física sobre a etiologia das doenças crônicas, pretendemos revelar o imenso potencial do exercício físico como agente terapêutico.Physical inactivity is strongly related to the incidence and severity of a number of chronic diseases. Hence, physical exercise emerges as one of the most important therapeutic tool to health promotion, with the Physical Education professional being the responsible for disseminating it widely. In this manuscript, we will discuss the following questions: 1) What is the social and biological impact of physical inactivity on overall health? 2) What is the impact of physical activity on people's lives? 3) What is the role of the Physical Education professional in the promotion of health and what are the challenges that Physical Education Discipline, as a science ("lato sensu") and profession, will face in the next decades? Having in mind the role of physical inactivity upon the etiology of chronic diseases, we intend to reveal the large potential of physical exercise as a therapeutic agent

Search for H→γγ produced in association with top quarks and constraints on the Yukawa coupling between the top quark and the Higgs boson using data taken at 7 TeV and 8 TeV with the ATLAS detector

A search is performed for Higgs bosons produced in association with top quarks using the diphoton decay mode of the Higgs boson. Selection requirements are optimized separately for leptonic and fully hadronic final states from the top quark decays. The dataset used corresponds to an integrated luminosity of 4.5 fb−14.5 fb−1 of proton–proton collisions at a center-of-mass energy of 7 TeV and 20.3 fb−1 at 8 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. No significant excess over the background prediction is observed and upper limits are set on the tt¯H production cross section. The observed exclusion upper limit at 95% confidence level is 6.7 times the predicted Standard Model cross section value. In addition, limits are set on the strength of the Yukawa coupling between the top quark and the Higgs boson, taking into account the dependence of the tt¯H and tH cross sections as well as the H→γγ branching fraction on the Yukawa coupling. Lower and upper limits at 95% confidence level are set at −1.3 and +8.0 times the Yukawa coupling strength in the Standard Model