1,461 research outputs found
PT Symmetry of the non-Hermitian XX Spin-Chain: Non-local Bulk Interaction from Complex Boundary Fields
The XX spin-chain with non-Hermitian diagonal boundary conditions is shown to
be quasi-Hermitian for special values of the boundary parameters. This is
proved by explicit construction of a new inner product employing a
"quasi-fermion" algebra in momentum space where creation and annihilation
operators are not related via Hermitian conjugation. For a special example,
when the boundary fields lie on the imaginary axis, we show the spectral
equivalence of the quasi-Hermitian XX spin-chain with a non-local fermion
model, where long range hopping of the particles occurs as the non-Hermitian
boundary fields increase in strength. The corresponding Hamiltonian
interpolates between the open XX and the quantum group invariant XXZ model at
the free fermion point. For an even number of sites the former is known to be
related to a CFT with central charge c=1, while the latter has been connected
to a logarithmic CFT with central charge c=-2. We discuss the underlying
algebraic structures and show that for an odd number of sites the superalgebra
symmetry U(gl(1|1)) can be extended from the unit circle along the imaginary
axis. We relate the vanishing of one of its central elements to the appearance
of Jordan blocks in the Hamiltonian.Comment: 37 pages, 5 figure
Enhancement of bichromatic high-harmonic generation with a high-frequency field
Using a high-frequency field superposed to a linearly polarized bichromatic
laser field composed by a wave with frequency and a wave with
frequency , we show it is possible to enhance the intensity of a
group of high harmonics in orders of magnitude. These harmonics have
frequencies about 30% higher than the monochromatic-cutoff frequency, and,
within the three-step-model framework, correspond to a set of electron
trajectories for which tunneling ionization is strongly suppressed. Particular
features in the observed enhancement suggest that the high-frequency field
provides an additional mechanism for the electron to reach the continuum. This
interpretation is supported by a time-frequency analysis of the harmonic yield.
The additional high frequency field permits the control of this group of
harmonics leaving all other sets of harmonics practically unchanged, which is
an advantage over schemes involving only bichromatic fields.Comment: 6 pages RevTex, 5 figures (ps files), Changes in text, figures,
references and equations include
Genetic correlations estimate between meat tenderness, growth and carcass traits in a population of polled nellore cattle in Brazil.
Growth, carcass and tenderness data from 415 Polled Nellore animals were analyzed in order to estimate the genetic correlations between tenderness (WBSF) and growth (ILW, FLW and ADG) and carcass (BF, RF and LMA) traits. The covariance components and genetic parameters were estimated using the Gibbs Sampling method. The heritability estimated for WBSF was of low magnitude (0.11 ± 0.022). The genetic correlations between WBSF and the other traits were of low magnitude, with values of - 0.15; -0.18; -0.13; 0.10; -0.12 and 0.18, between WBSF and ILW, FLW, ADG, BF, RF and LMA, respectively. The results support the conclusion that selection for improved tenderness will not affect genetic progress in other economic traits and vice-versa, but more studies are required for a better knowledge of the genetic relationships between meat tenderness and other traits for Polled Nellore cattle
Time Evolution of tunneling and decoherence: soluble model
Decoherence effects associated to the damping of a tunneling two-level system
are shown to dominate the tunneling probability at short times in strong
coupling regimes in the context of a soluble model. A general decomposition of
tunneling rates in dissipative and unitary parts is implemented. Master
equation treatments fail to describe the model system correctly when more than
a single relaxation time is involved
Perturbation theory of PT-symmetric Hamiltonians
In the framework of perturbation theory the reality of the perturbed
eigenvalues of a class of \PTsymmetric Hamiltonians is proved using stability
techniques. We apply this method to \PTsymmetric unperturbed Hamiltonians
perturbed by \PTsymmetric additional interactions
Avaliação genética de características de carcaça utilizando a técnica do ultrassom em bovinos de corte.
bitstream/item/58229/1/DT115.pd
Comparative chromosome painting discloses homologous Segments in distantly related mammals
Comparative chromosome painting, termed ZOO-FISH, using DNA libraries from flow
sorted human chromosomes 1,16,17 and X, and mouse chromosome 11 discloses the
presence of syntenic groups in distantly related mammalian Orders ranging from
primates (Homo sapiens), rodents (Mus musculus), even-toed ungulates (Muntiacus
muntjak vaginalis and Muntiacus reevesi) and whales (Balaenoptera physalus). These
mammalian Orders have evolved separately for 55-80 million years (Myr). We conclude
that ZOO-FISH can be used to generate comparative chromosome maps of a large
number of mammalian species
Common bean white mold resistance sources identified by greenhouse screening in Brazil.
The main goal of the present work was to evaluate the reaction of 39 common bean lines to white mold in a greenhouse screening. These bean genotypes include Brazilian cultivars and advanced lines from different market classes, in addition to resistance sources previously reported by CIAT (Cali, Colombia). The effective identification of resistance sources and superior genotypes is a basic and continuous step of breeding efforts aiming to develop/select resistant cultivars to be used in the integrated control of white mold
Valor nutritivo da dieta de bovinos de corte mantidos em pastagem natural com diferentes níveis de intensificação.
Avaliação do componente genético na expressão fenotípica de características produtivas de bovinos nelore submetidos à prova de desempenho.
Objetivou-se avaliar o efeito do componente genético na expressão fenotípica de características produtivas de bovinos da raça Nelore submetidos à prova de desempenho individual. Os dados utilizados foram provenientes de 51 touros jovens participantes da Prova de Desempenho Individual de Touros Nelore realizada na fazenda experimental Capim Branco da Universidade Federal de Uberlândia. As características avaliadas foram peso e perímetro escrotal padronizado aos 365 e aos 450 dias de idade, área de olho de lombo e acabamento de carcaça. Com o intuito de avaliar a contribuição do componente genético no desempenho produtivo dos animais foram consideradas as predições das diferenças esperadas na progênie dos animais e dos touros (pais dos animais). Para verificar os efeitos dos grupos genéticos sobre o desempenho produtivo foram realizadas análises de variância por meio do procedimento General Linear Model do aplicativo Statistical Analysis System. Verificou-se que os filhos de touros com maior potencial genético tendem a apresentar melhor desempenho produtivo. Concluiu-se que o uso de animais geneticamente superiores permite a obtenção de melhores índices zootécnicos refletindo em maiores ganhos em produtividade do rebanho
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