3,225 research outputs found

    On topological spin excitations on a rigid torus

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    We study Heisenberg model of classical spins lying on the toroidal support, whose internal and external radii are rr and RR, respectively. The isotropic regime is characterized by a fractional soliton solution. Whenever the torus size is very large, RR\to\infty, its charge equals unity and the soliton effectively lies on an infinite cylinder. However, for R=0 the spherical geometry is recovered and we obtain that configuration and energy of a soliton lying on a sphere. Vortex-like configurations are also supported: in a ring torus (R>rR>r) such excitations present no core where energy could blow up. At the limit RR\to\infty we are effectively describing it on an infinite cylinder, where the spins appear to be practically parallel to each other, yielding no net energy. On the other hand, in a horn torus (R=rR=r) a singular core takes place, while for R<rR<r (spindle torus) two such singularities appear. If RR is further diminished until vanish we recover vortex configuration on a sphere.Comment: 11 pages, 9 figure

    Berry phases and zero-modes in toroidal topological insulator

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    An effective Hamiltonian describing the surface states of a toroidal topological insulator is obtained, and it is shown to support both bound-states and charged zero-modes. Actually, the spin connection induced by the toroidal curvature can be viewed as an position-dependent effective vector potential, which ultimately yields the zero-modes whose wave-functions harmonically oscillate around the toroidal surface. In addition, two distinct Berry phases are predicted to take place by the virtue of the toroidal topology.Comment: New version, accepted for publication in EPJB, 6 pages, 1 figur

    Genetics and expected selection gain for growth traits in Eugenia dysenterica DC populations.

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    The objective of this study was to estimate genetic parameters of quantitative traits in a living germplasm collection of Eugenia dysenterica. The genetic material consisted of 110 progenies derived from 10 natural Eugenia dysenterica subpopulations sampled in the southeastern region of the state of Goiás. The experiment was established in a complete randomized block design, with 110 treatments, four replications and one tree per plot. The study variables were total height, stem diameter and respective growth rates. After the analysis of variance some genetic parameters were estimated. The levels of genetic variation in the collection were high and the highest proportion was found within subpopulations. Highest coefficients of heritability and genetic variation were observed in subpopulations from the counties Catalão, Três Ranchos, Cristalina and Senador Canedo. Considering the promising expected progress for growth traits, this collection can be converted into an unrogued seedling seed orchard, aiming the production of improved seed

    On Deciding Local Theory Extensions via E-matching

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    Satisfiability Modulo Theories (SMT) solvers incorporate decision procedures for theories of data types that commonly occur in software. This makes them important tools for automating verification problems. A limitation frequently encountered is that verification problems are often not fully expressible in the theories supported natively by the solvers. Many solvers allow the specification of application-specific theories as quantified axioms, but their handling is incomplete outside of narrow special cases. In this work, we show how SMT solvers can be used to obtain complete decision procedures for local theory extensions, an important class of theories that are decidable using finite instantiation of axioms. We present an algorithm that uses E-matching to generate instances incrementally during the search, significantly reducing the number of generated instances compared to eager instantiation strategies. We have used two SMT solvers to implement this algorithm and conducted an extensive experimental evaluation on benchmarks derived from verification conditions for heap-manipulating programs. We believe that our results are of interest to both the users of SMT solvers as well as their developers

    O uso de centeio como cultura intercalar em videiras.

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