2,630 research outputs found
Phase Transition and Monopoles Densities in a Nearest Neighbors Two-Dimensional Spin Ice Model
In this work, we show that, due to the alternating orientation of the spins
in the ground state of the artificial square spin ice, the influence of a set
of spins at a certain distance of a reference spin decreases faster than the
expected result for the long range dipolar interaction, justifying the use of
the nearest neighbor two dimensional square spin ice model as an effective
model. Using an extension of the model presented in ref. [Scientific Reports 5,
15875 (2015)], considering the influence of the eight nearest neighbors of each
spin on the lattice, we analyze the thermodynamics of the model and study the
monopoles and string densities dependence as a function of the temperature.Comment: 11 pages, 8 figure
Spin g-factor due to electronic interactions in graphene
The gyromagnetic factor is an important physical quantity relating the
magnetic-dipole moment of a particle to its spin. The electron spin g-factor in
vacuo is one of the best model-based theoretical predictions ever made, showing
agreement with the measured value up to ten parts per trillion. However, for
electrons in a material the g-factor is modified with respect to its value in
vacuo because of environment interactions. Here, we show how interaction
effects lead to the spin g-factor correction in graphene by considering the
full electromagnetic interaction in the framework of pseudo-QED. We compare our
theoretical prediction with experiments performed on graphene deposited on SiO2
and SiC, and we find a very good agreement between them.Comment: Improved version of the manuscript; valley g-factor part has been
remove
Signature of stripe pinning in optical conductivity
The response of charge stripes to an external electric field applied
perpendicular to the stripe direction is studied within a diagrammatic approach
for both weak and strong pinning by random impurities. The sound-like mode of
the stripes described as elastic strings moves to finite frequency due to
impurity pinning. By calculating the optical conductivity we determine this
characteristic energy scale for both a single stripe and an array of
interacting stripes. The results explain the anomalous far-infrared peak
observed recently in optical-conductivity measurements on cuprates.Comment: Revised version, to appear in Phys. Rev.
Difusão e validação de tecnologias para a sustentabilidade da agricultura familiar do Estado de Goiás.
O objetivo deste trabalho foi selecionar cultivares e linhagens de arroz e feijão adaptadas ao sistema de produção dos pequenos agricultores, por meio da implementação de ensaios de VCU (Valor de cultivo e uso) e unidades demonstrativas nas propriedades dos agricultores em Goiás; produzir sementes da variedade Samambaia e criar uma relação de cooperação entre pesquisadores e produtores, na qual o produtor familiar é colocado também na condição de pesquisador e responsável pela preservação dos recursos naturais
Cooking quality and physicochemical traits of upland rice with different amylose content.
The objective of this study is to characterize genotypes of upland rice with different amylose content regarding cooking quality by using different physicochemical tools.IRC14-0643
Correlation Effects in Ultracold Two-Dimensional Bose Gases
We study various properties of an ultracold two-dimensional (2D) Bose gas
that are beyond a mean-field description. We first derive the effective
interaction for such a system as realized in current experiments, which
requires the use of an energy dependent -matrix. Using this result, we then
solve the mean-field equation of state of the modified Popov theory, and
compare it with the usual Hartree-Fock theory. We show that even though the
former theory does not suffer from infrared divergences in both the normal and
superfluid phases, there is an unphysical density discontinuity close to the
Berezinskii-Kosterlitz-Thouless transition. We then improve upon the mean-field
description by using a renormalization group approach and show how the density
discontinuity is resolved. The flow equations in two dimensions, in particular,
of the symmetry-broken phase, already contain some unique features pertinent to
the 2D XY model, even though vortices have not been included explicitly. We
also compute various many-body correlators, and show that correlation effects
beyond the Hartree-Fock theory are important already in the normal phase as
criticality is approached. We finally extend our results to the inhomogeneous
case of a trapped Bose gas using the local-density approximation and show that
close to criticality, the renormalization group approach is required for the
accurate determination of the density profile.Comment: 11 pages, 12 figure
Atividade antifúngica de óleos essenciais em sementes de feijão cv. Carioquinha.
Este trabalho teve por objetivo avaliar o efeito de óleos essenciais de manjericão (Ocimum sp.), dois tipos de capim limão (Cymbopogon flexuosus e C. citratus) e melaleuca (Melaleuca sp.), na germinação e sanidade de sementes de feijão
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