11,211 research outputs found
Nuclear Magnetic Relaxation Rate in a Noncentrosymmetric Superconductor
For a noncentrosymmetric superconductor such as CePt3Si, we consider a Cooper
pairing model with a two-component order parameter composed of spin-singlet and
spin-triplet pairing components.
We demonstrate that such a model on a qualitative level accounts for
experimentally observed features of the temperature dependence of the nuclear
spin-lattice relaxation rate 1/T1, namely a peak just below Tc and a line-node
gap behavior at low temperatures.Comment: 4 page
Detecção de Potyvirus em bucha (Luffa cylindrica (L.) Roem.) no estado do Pará.
A bucha (Luffa cyllindrica (L.) Roem.) é uma trepadeira da família das cucurbitáceas cultivada especialmente pelas fibras do fruto seco, que tem vários usos principalmente como esfregão de banho. Folhas de plantas apresentando mosaico amarelo no município de Baião foram coletadas levadas para proceder a diagnose no laboratório de fitopatologia da Embrapa Amazônia Oriental. Para a identificação do vírus foi realizado o teste sorológico PTA-ELISA onde se testou a amostra da bucha contra os antissoros específicos para Cucumber mosaic virus (CMV), Watermelon mosaic virus (WMV), Zucchini yellow mosaic virus (ZYMV) e Squash mosaic virus (SMV). Extrato da folha da bucha com mosaico reagiu positivamente com o antissoro do ZYMV indicando se tratar de potyvirus. Assim, a comprovação de que o mosaico da bucha é causado por potyvirus foi feita via RT-PCR utilizando primers específico para o gênero. Além da sorologia foi realizada a purificação parcial do vírus, extração de RNA viral seguido do RT-PCR onde utilizou o par de primers universal (WCIEN e PV1) para espécies virais do gênero Potyvirus. Após eletroforese para análise do produto da RT-PCR observou-se a presença do fragmento de DNA do tamanho esperado de aproximadamente 800 pb confirmando a presença de potyvirus. Plantas de bucha infectadas podem servir de fonte de inóculo para outras plantas cultivadas como abóbora e pepin
Identificação de Cucumber mosaic virus em pimenta no estado do Pará.
A pimenta (Capsicum chinense e C. frutescens) é bastante cultivada no estado do Pará, mas algumas doenças podem limitar sua produção. É comum observar plantas com sintomas de viroses. Assim, este trabalho tem o objetivo de identificar os vírus que ocorrem em plantios de pimenta. Foram coletadas amostras de plantios no município de Santa Izabel e em Belém. Para isso, foi realizada a inoculação em plantas indicadoras, extração de acido nucleico, os testes de RT-PCR e sequenciamento nucleotídico. Foram analisadas quatro amostras provenientes de Santa Izabel e duas de Belém. Os isolados virais foram transmitidos mecanicamente para plantas indicadoras de vírus Nicotiana tabacco cv. TNN e N. tabacum cv. Turkish que apresentaram mosaico foliar. A partir de folhas infectadas de fumo foi feita a extração do ácido nucléico total. Posteriormente, foi feito o teste de RT-PCR, utilizando os pares de primers CMV-CPR e CMV-CPF para detecção de Cucumber mosaic virus ? CMV e PV1 e WCIEN para espécies do gênero Potyvirus. As amostras foram positivas para o CMV, pois amplificaram o gene da capa proteica de aproximadamente 700pb. O produto PCR de dois isolados (Belém e Santa Izabel) foram sequenciados e analisados utilizando os programas Blast e ClustalW. Os dois isolados apresentaram identidade de aminoácido de 98% quando comparados com acessos disponíveis no GenBank. Este foi o primeiro relato de Cucumber mosaic virus no estado do Pará. Até o momento foi identificado apenas o CMV em pimentais no Pará, sendo este considerado um dos principais vírus relatados no Brasil no gênero Capsicum sp
Positions of Point-Nodes in Borocarbide Superconductor YNi2B2C
To determine the superconducting gap function of YNi2B2C, we calculate the
local density of states (LDOS) around a single vortex core with the use of
Eilenberger theory and the band structure calculated by local density
approximation assuming various gap structures with point-nodes at different
positions. We also calculate the angular-dependent heat capacity in the vortex
state on the basis of the Doppler-Shift method. Comparing our results with the
STM/STS experiment, the angular-dependent heat capacity and thermal
conductivity, we propose the gap-structure of YNi2B2C, which has the
point-nodes and gap minima along . Our gap-structure is consistent with
all results of angular-resolved experiments.Comment: 7 pages, 5 figure
Surface and vortex structures in noncentrosymmetric superconductors under applied magnetic fields
We investigate how the macroscopic spatial structure of broken inversion
symmetry manifests in noncentrosymmetric superconductors, by the microscopic
broken inversion symmetry of the crystal structure. Based on the time-dependent
Ginzburg-Landau theory including the Pauli paramagnetic effect and the Rashba
interaction, we demonstrate that the centrosymmetric structures of the internal
field and the screening current are broken macroscopically. The flow structure
of paramagnetic supercurrent spontaneously induce the flux flow without
applying external currents.Comment: 5 pages, 8 figures. accepted in Phys. Rev.
Nonuniform Spin Triplet Superconductivity due to Antisymmetric Spin-Orbit Coupling in Noncentrosymmetric Superconductor CePtSi
We show that the nonuniform state (Fulde-Ferrel-Larkin-Ovchinnikov (FFLO)
state) of the spin triplet superconductivity in noncentrosymmetric systems is
stabilized by antisymmetric spin-orbit coupling even if the magnetic field is
absent. The transition temperature of the spin triplet superconductivity is
reduced by the antisymmetric spin-orbit coupling in general. This pair breaking
effect is shown to be similar to the Pauli pair breaking effect due to magnetic
field for the spin singlet superconductivity, in which FFLO state is stabilized
near the Pauli limit (or Chandrasekhar-Clogston limit) of external magnetic
field. Since there are gapless excitations in nonuniform superconducting state,
some physical quantities such as specific heat and penetration depth should
obey the power low temperature-dependences. We discuss the possibility of the
realization of nonuniform state in CePtSi.Comment: 8 pages, 6 figure
Locally Weyl invariant massless bosonic and fermionic spin-1/2 action in the and space-times
We search for a real bosonic and fermionic action in four dimensions which
both remain invariant under local Weyl transformations in the presence of
non-metricity and contortion tensor. In the presence of the non-metricity
tensor the investigation is extended to Weyl space-time while when
the torsion is encountered we are restricted to the Riemann-Cartan
space-time. Our results hold for a subgroup of the Weyl-Cartan
space-time and we also calculate extra contributions to the conformal gravity.Comment: 16 page
Analytical Formulation of the Local Density of States around a Vortex Core in Unconventional Superconductors
On the basis of the quasiclassical theory of superconductivity, we obtain a
formula for the local density of states (LDOS) around a vortex core of
superconductors with anisotropic pair-potential and Fermi surface in arbitrary
directions of magnetic fields. Earlier results on the LDOS of d-wave
superconductors and NbSe are naturally interpreted within our theory
geometrically; the region with high intensity of the LDOS observed in numerical
calculations turns out to the enveloping curve of the trajectory of Andreev
bound states. We discuss experimental results on YNiBC within the
quasiclassical theory of superconductivity.Comment: 13 pages, 16 figure
Ds0*(2317) and Ds1(2460) mesons in two-body B-meson decays
We analyze the branching ratios of B to D(*) + Ds0*(Ds1) decays using the
factorization hypothesis. The B to D(*) transition form factors are taken from
a model-independent analysis done by Caprini, Lellouch and Neubert based on
heavy quark spin symmetry and dispersive constraints, including short-distance
and power corrections. The leptonic decay constants fDs0* and fDs1 are
calculated assuming a molecular structure for the Ds0* and Ds1 mesons. The
calculated branching ratios of B-meson two-body decays are compared with
experimental data and other theoretical results.Comment: 12 pages, 2 figure
The quantum Chernoff bound as a measure of distinguishability between density matrices: application to qubit and Gaussian states
Hypothesis testing is a fundamental issue in statistical inference and has
been a crucial element in the development of information sciences. The Chernoff
bound gives the minimal Bayesian error probability when discriminating two
hypotheses given a large number of observations. Recently the combined work of
Audenaert et al. [Phys. Rev. Lett. 98, 160501] and Nussbaum and Szkola
[quant-ph/0607216] has proved the quantum analog of this bound, which applies
when the hypotheses correspond to two quantum states. Based on the quantum
Chernoff bound, we define a physically meaningful distinguishability measure
and its corresponding metric in the space of states; the latter is shown to
coincide with the Wigner-Yanase metric. Along the same lines, we define a
second, more easily implementable, distinguishability measure based on the
error probability of discrimination when the same local measurement is
performed on every copy. We study some general properties of these measures,
including the probability distribution of density matrices, defined via the
volume element induced by the metric, and illustrate their use in the
paradigmatic cases of qubits and Gaussian infinite-dimensional states.Comment: 16 page
- …