A Two-Form Formulation of the Vector-Tensor Multiplet in Central Charge Superspace

A two-form formulation for the N=2 vector-tensor multiplet is constructed using superfield methods in central charge superspace. The N=2 non-Abelian standard supergauge multiplet in central charge superspace is also discussed, as is with the associated Chern-Simons form. We give the constraints, solve the Bianchi identities and present the action for a theory of the vector-tensor multiplet coupled to the non-Abelian supergauge multiplet via the Chern-Simons form.Comment: 16 pages, LaTeX2e with AMS-LaTe

Vector-Tensor multiplet in N=2 superspace with central charge

We use the four-dimensional N=2 central charge superspace to give a geometrical construction of the Abelian vector-tensor multiplet consisting, under N=1 supersymmetry, of one vector and one linear multiplet. We derive the component field supersymmetry and central charge transformations, and show that there is a super-Lagrangian, the higher components of which are all total derivatives, allowing us to construct superfield and component actions.Comment: LaTeX2e with AMS-LaTeX, 12 page

Heuristic Models of Two-Fermion Relativistic Systems with Field-Type Interaction

We use the chain of simple heuristic expedients to obtain perturbative and exactly solvable relativistic spectra for a family of two-fermionic bound systems with Coulomb-like interaction. In the case of electromagnetic interaction the spectrum coincides up to the second order in a coupling constant with that following from the quantum electrodynamics. Discrepancy occurs only for S-states which is the well-known difficulty in the bound-state problem. The confinement interaction is considered too. PACS number(s): 03.65.Pm, 03.65.Ge, 12.39.PnComment: 16 pages, LaTeX 2.0

Classical and Quantum Analysis of Repulsive Singularities in Four Dimensional Extended Supergravity

Non--minimal repulsive singularities (``repulsons'') in extended supergravity theories are investigated. The short distance antigravity properties of the repulsons are tested at the classical and the quantum level by a scalar test--particle. Using a partial wave expansion it is shown that the particle gets totally reflected at the origin. A high frequency incoming particle undergoes a phase shift of $\frac{\pi}{2}$. However, the phase shift for a low--frequency particle depends upon the physical data of the repulson. The curvature singularity at a finite distance $r_h$ turns out to be transparent for the scalar test--particle and the coordinate singularity at the origin serves as a repulsive barrier at which particles bounce off.Comment: 20 pages, 14 figure

Non-Supersymmetric Charged Domain Walls

We present general non-supersymmtric domain wall solutions with non-trivial scalar and gauge fields for gauged five-dimensional N=2 supergravity coupled to abelian vector multiplets.Comment: 11 pages, one ref. added. To appear in Physics Letters

Ultrafast sublattice pseudospin relaxation in graphene probed by polarization-resolved photoluminescence

Electronic pseudospin degrees of freedom in two-dimensional materials exhibit unique carrier-field interactions which allow for advanced control strategies. Here, we investigate ultrafast sublattice pseudospin relaxation in graphene by means of polarization-resolved photoluminescence spectroscopy. A comparison with microscopic Boltzmann simulations allows us to determine a lifetime of the optically aligned pseudospin distribution of 12±2fs. This experimental approach extends the toolbox of graphene pseudospintronics, providing additional means to investigate pseudospin dynamics in active devices or under external fields

Professores orientadores de Estágio Curricular: aspectos relativos à aprendizagem e à identificação com a atividade de orientação

The article aims to understand auxiliary aspects in the learning of supervision of Curricular Training (CT) in Teacher Education Courses (TEC), as well in the supervising professors’ identifi cation with the activity of supervision. For this purpose, individual structured interviews were made with 25 supervising professors of TEC of the Federal University of Santa Maria, Brazil. The interviews were then analyzed using procedures of Content Analysis (Bardin, 1977). On the basis of these procedures, it was perceived that the supervising professors had very different educational and professional careers, which can enrich the interaction among them if their differences are respected and negotiated. In general, the supervisors’ identifi cation with their activity depends on a previous interest of  working in it or on experiences considered as preparatory to  supervise CT. Both thelearning and the identifi cation with the activity of supervision are autonomous processes for the supervisor, with no institutional participation. Thus, the identity formation of these supervising professors depends on having previous experiences related to CT supervision, on being welcomed by a more experienced supervisor colleague and, in other cases, by having motivation to look for literature and/or to dialogue with other professionals.Key words: supervising professor of curricular training, professional identity, curricular trainingsupervision, secondary socialization.O presente estudo visou compreender aspectos auxiliares na aprendizagem da atividade de orientação de Estágio Curricular (EC) em Cursos de Licenciatura (CL) bem como na identificaçãodos professores orientadores de EC com essa atividade. Para isso, foram realizadas entrevistas estruturadas individuais com 25 professores orientadores atuantes em CL da Universidade Federal de Santa Maria (UFSM/RS), as quais foram analisadas mediante procedimentos apresentados na Análise de Conteúdo (Bardin, 1977). A partir desses procedimentos, percebeu-se que os professores orientadores apresentam trajetórias formativas e atuações profissionais bem distintas, podendo isso enriquecer a interação entre eles, desde que respeitadas e negociadas as diferenças. Em geral, a identificação com a atividade de orientação depende de uma intenção prévia de realizá-la ou da vivência de experiências tidas como preparatórias para orientar EC. Tanto a aprendizagem quanto a identificação do orientador com essa atividade são processosautônomos para o orientador, sem participação institucional. Assim, a formação identitária desses professores orientadores está condicionada à vivência de experiências prévias relacionadas com orientação de EC; à recepção por um colega orientador mais experiente; e, em outros casos, à motivação própria para buscar leituras e/ou dialogar com outros profissionais.Palavras-chave: professor orientador de Estágio Curricular, identidade profi ssional, orientaçãode Estágio Curricular, socialização secundária

Black Holes and Flop Transitions in M-Theory on Calabi-Yau Threefolds

We present fivedimensional extreme black hole solutions of M-theory compactified on Calabi-Yau threefolds and study these solutions in the context of flop transitions in the extended Kahler cone. In particular we consider a specific model and present black hole solutions, breaking half of N=2 supersymmetry, in two regions of the extended Kahler cone, which are connected by a flop transition. The conditions necessary to match both solutions at the flop transition are analysed. Finally we also discuss the conditions to obtain massless black holes at the flop transition.Comment: 19 pp, LaTe

Ultrafast electron microscopy for probing magnetic dynamics

The spatial features of ultrafast changes in magnetic textures carry detailed information on microscopic couplings and energy transport mechanisms. Electrons excel in imaging such picosecond or shorter processes at nanometer length scales. We review the range of physical interactions that produce ultrafast magnetic contrast with electrons, and specifically highlight the recent emergence of ultrafast Lorentz transmission electron microscopy. From the fundamental processes involved in demagnetization at extremely short timescales to skyrmion-based devices, we show that ultrafast electron imaging will be a vital tool in solving pressing problems in magnetism and magnetic materials where nanoscale inhomogeneity, microscopic field measurement, non-equilibrium behavior or dynamics are involved

Carbon chloride-core fibers for soliton mediated supercontinuum generation

We report on soliton-fission mediated infrared supercontinuum generation in liquid-core step-index fibers using highly transparent carbon chlorides (CCl4, C2Cl4). By developing models for the refractive index dispersions and nonlinear response functions, dispersion engineering and pumping with an ultrafast thulium fiber laser (300 fs) at 1.92 μm, distinct soliton fission and dispersive wave generation was observed, particularly in the case of tetrachloroethylene (C2Cl4). The measured results match simulations of both the generalized and a hybrid nonlinear Schrödinger equation, with the latter resembling the characteristics of non-instantaneous medium via a static potential term and representing a simulation tool with substantially reduced complexity. We show that C2Cl4 has the potential for observing non-instantaneous soliton dynamics along meters of liquid-core fiber opening a feasible route for directly observing hybrid soliton dynamics