Vortex Viscosity in Magnetic Superconductors Due to Radiation of Spin Waves

In type-II superconductors that contain a lattice of magnetic moments, vortices polarize the magnetic system inducing additional contributions to the vortex mass, vortex viscosity, and vortex-vortex interaction. Extra magnetic viscosity is caused by radiation of spin waves by a moving vortex. Like in the case of Cherenkov radiation, this effect has a characteristic threshold behavior and the resulting vortex viscosity may be comparable to the well-known Bardeen-Stephen contribution. The threshold behavior leads to an anomaly in the current-voltage characteristics, and a drop in dissipation for a current interval that is determined by the magnetic excitation spectrum.Comment: 4 pages, 1 figur

Unveiling Order behind Complexity: Coexistence of Ferromagnetism and Bose-Einstein Condensation

We present an algebraic framework for identifying the order parameter and the possible phases of quantum systems that is based on identifying the local dimension $N$ of the quantum operators and using the SU(N) group representing the generators of generalized spin-particle mappings. We illustrate this for $N$=3 by presenting for any spatial dimension the exact solution of the bilinear-biquadratic $S$=1 quantum Heisenberg model at a high symmetry point. Through this solution we rigorously show that itinerant ferromagnetism and Bose-Einstein condensation may coexist.Comment: 5 pages, 1 psfigur

Bioeletricidade no setor sucroalcooleiro paulista: participação no mercado de carbono, perspectivas e sustentabilidade.

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Efeito de variáveis ambientais na implantação do sistema de inseminação artificial no Pantanal.

A pecuária de corte é a principal atividade econômica desenvolvida na planície Pantaneira. A implantação da inseminação artificial é indispensável para o aprimoramento da bovinocultura de corte, principalmente, quando se quer estabelecer um programa de melhoramento genético animal, com objetivo de alcançar maior produtividade. The beef cattle is the principal economical activity developed in the plain Pantaneira. The introduction of the artificial insemination (AI) that is essential for the improvement of the beef cattle, principally, when there wants to be introduced a program of genetic animal improvement and to reach bigger profit with the cattle as a whole

Phonon Thermal Transport of URu2Si2: Broken Translational Symmetry and Strong-Coupling of the Hidden Order to the Lattice

A dramatic increase in the total thermal conductivity (k) is observed in the Hidden Order (HO) state of single crystal URu2Si2. Through measurements of the thermal Hall conductivity, we explicitly show that the electronic contribution to k is extremely small, so that this large increase in k is dominated by phonon conduction. An itinerant BCS/mean-field model describes this behavior well: the increase in kappa is associated with the opening of a large energy gap at the Fermi Surface, thereby decreasing electron-phonon scattering. Our analysis implies that the Hidden Order parameter is strongly coupled to the lattice, suggestive of a broken symmetry involving charge degrees of freedom.Comment: 17 pages including figures, updated author institutions and acknowledgement

Load-Balancing for Parallel Delaunay Triangulations

Computing the Delaunay triangulation (DT) of a given point set in $\mathbb{R}^D$ is one of the fundamental operations in computational geometry. Recently, Funke and Sanders (2017) presented a divide-and-conquer DT algorithm that merges two partial triangulations by re-triangulating a small subset of their vertices - the border vertices - and combining the three triangulations efficiently via parallel hash table lookups. The input point division should therefore yield roughly equal-sized partitions for good load-balancing and also result in a small number of border vertices for fast merging. In this paper, we present a novel divide-step based on partitioning the triangulation of a small sample of the input points. In experiments on synthetic and real-world data sets, we achieve nearly perfectly balanced partitions and small border triangulations. This almost cuts running time in half compared to non-data-sensitive division schemes on inputs exhibiting an exploitable underlying structure.Comment: Short version submitted to EuroPar 201

Alguns aspectos da eficiência reprodutiva no rebanho nelore da Estação Experimental do Pantanal.

Foram avaliadas as taxas de prenhez de vacas da raça Nelore das categorias nulíparas, primíparas e multíparas, a partir de dados provenientes de quatro estações de inseminações de uma fazenda com sistema extensivo de cria, tendo como base pastagens nativas típicas da região do Pantanal. As taxas de prenhez foram agrupadas em tabela de contingência e analisadas pelo teste de qui-quadrado. E para ilustração utilizou-se o método de box-plot. Para as categorias nulíparas, primíparas e multíparas, as médias das taxas de prenhez foram de 84%, 43% e 47%, respectivamente. Sendo que a taxa de prenhez das nulíparas foi maior (P0,05) entre si. Portanto, para aumentar a eficiência da inseminação artificial nas condições extensivas do Pantanal, são necessárias melhorias no sistema de manejo que otimizem maiores taxas de prenhez. Were evaluated the pregnancy rates of the cows of Nelore race, from data of four stations of inseminations (SI), categories nulliparous, primiparous and multiparous, of a farm with an extensive cow-calf system, based on native pastures typical of the region of the Pantanal. Pregnancy rates were grouped into a contingency table and analyzed by chi-square. And for illustration, we used the method of box-plot. The average pregnancy rate was 84%, 43% and 47% for category nulliparous, primiparous and multiparous, respectively. The pregnancy rate of nulliparous was higher (P 0.05) between them. Therefore to increase the efficiency of artificial insemination in the conditions of the Pantanal improvements are needed in the system of management that optimize higher pregnancy rates

Vortex-induced dissipation in narrow current-biased thin-film superconducting strips

A vortex crossing a thin-film superconducting strip from one edge to the other, perpendicular to the bias current, is the dominant mechanism of dissipation for films of thickness d on the order of the coherence length XI; and of width w much narrower than the Pearl length LAMBDA >> w >> XI. At high bias currents, I* < I < Ic, the heat released by the crossing of a single vortex suffices to create a belt-like normal-state region across the strip, resulting in a detectable voltage pulse. Here Ic is the critical current at which the energy barrier vanishes for a single vortex crossing. The belt forms along the vortex path and causes a transition of the entire strip into the normal state. We estimate I* to be roughly Ic/3. Further, we argue that such "hot" vortex crossings are the origin of dark counts in photon detectors, which operate in the regime of metastable superconductivity at currents between I* and Ic. We estimate the rate of vortex crossings and compare it with recent experimental data for dark counts. For currents below I*, i.e., in the stable superconducting but resistive regime, we estimate the amplitude and duration of voltage pulses induced by a single vortex crossing.Comment: 9 pages, 3 figure

Exact Bond Ordered Ground State for the Transition Between the Band and the Mott Insulator

We derive an effective Hamiltonian $H_{eff}$ for an ionic Hubbard chain, valid for $t\ll U,\Delta$, where $t$ is the hopping, $U$ the Coulomb repulsion, and $\Delta$ the charge transfer energy. $H_{eff}$ is the minimal model for describing the transition from the band insulator (BI) ($\Delta -U\gg t$) and the Mott insulator (MI) ($U-\Delta \gg t$). Using spin-particle transformations (Phys. Rev. Lett. \textbf{86}, 1082 (2001)), we map $H_{eff}(U=\Delta)$ into an SU(3) antiferromagnetic Heisenberg model whose exact ground state is known. In this way, we show rigorously that a spontaneously dimerized insulating ferroelectric phase appears in the transition region between the BI and MI