22,059 research outputs found
Multipartite Entanglement Signature of Quantum Phase Transitions
We derive a general relation between the non-analyticities of the ground
state energy and those of a subclass of the multipartite generalized global
entanglement (GGE) measure defined by T. R. de Oliveira et al. [Phys. Rev. A
73, 010305(R) (2006)] for many-particle systems. We show that GGE signals both
a critical point location and the order of a quantum phase transition (QPT). We
also show that GGE allows us to study the relation between multipartite
entanglement and QPTs, suggesting that multipartite but not bipartite
entanglement is favored at the critical point. Finally, using GGE we were able,
at a second order QPT, to define a diverging entanglement length (EL) in terms
of the usual correlation length. We exemplify this with the XY spin-1/2 chain
and show that the EL is half the correlation length.Comment: Published version. Incorporates correction made in erratu
Genuine Multipartite Entanglement in Quantum Phase Transitions
We demonstrate that the Global Entanglement (GE) measure defined by Meyer and
Wallach, J. Math. Phys. 43, 4273 (2002), is maximal at the critical point for
the Ising chain in a transverse magnetic field. Our analysis is based on the
equivalence of GE to the averaged linear entropy, allowing the understanding of
multipartite entanglement (ME) features through a generalization of GE for
bipartite blocks of qubits. Moreover, in contrast to GE, the proposed ME
measure can distinguish three paradigmatic entangled states: ,
, and . As such the generalized measure can detect
genuine ME and is maximal at the critical point.Comment: 4 pages, 3 figures. Replaced with final published versio
Fourier Eigenfunctions, Uncertainty Gabor Principle and Isoresolution Wavelets
Shape-invariant signals under Fourier transform are investigated leading to a
class of eigenfunctions for the Fourier operator. The classical uncertainty
Gabor-Heisenberg principle is revisited and the concept of isoresolution in
joint time-frequency analysis is introduced. It is shown that any Fourier
eigenfunction achieve isoresolution. It is shown that an isoresolution wavelet
can be derived from each known wavelet family by a suitable scaling.Comment: 6 pages, XX Simp\'osio Bras. de Telecomunica\c{c}\~oes, Rio de
Janeiro, Brazil, 2003. Fixed typo
The mechanism for the electrooxidation of procarbazine pharmaceutical preparation in alkaline media and its mathematical description
The mechanism for the electrooxidation of procarbazine in alkaline media has been proposed. The process is realized completely on the electrode surface and is adsorption-controlled. The oscillatory behavior in this case is more probable, than for neutral media and may be caused by influences of electrochemical oxidation and salt dissolution from the electrode surface
Variedade de milho melhora renda e segurança alimentar de agricultores familiares.
bitstream/item/67266/1/Vmilho0001.pdfPublicado em: Boletim Pecuário; Grupo Cultivar; Webartigos.com; Portal do Agronegócio
Produção e distribuição de biomassa de espécies arbóreas no Semi-Árido brasileiro.
Com o objetivo de avaliar a produção e distribuição de biomassa de algumas espécies arbóreas de múltiplo uso em condições de sequeiro do submédio do São Francisco, instalou-se um experimento no Campo Experimental da Caatinga da Embrapa Semi-Árido, Município de Petrolina, PE. Foram realizadas medições de altura e diâmetro à altura do peito (DAP) de 16 árvores centrais, em três parcelas de cada espécie: Leucaena diversifolia, Caesalpinia velutina, Caesalpinia coriaria, Mimosa tenuiflora e Ateleia herbert-smithii. A biomassa foi estimada com base na árvore de altura média de cada parcela, avaliando-se, separadamente, cada componente (folhas, galhos, cascas e lenho). A biomassa nos diferentes componentes arbóreos das espécies foi distribuída na seguinte ordem: folha<casca<galho<raiz<lenho, excetuando-se A. herbert-smithii, que produziu mais folha do que casca. A produção de biomassa total foi superior em C. velutina (51,6 kg ha-1), seguida por L. diversifolia (36,6 kg ha-1), A. herbert-smithii (26,4 kg ha-1), Caesalpinia coriaria (23,0 kg ha-1) e Mimosa tenuiflora (21,6 kg ha-1). Entretanto, a matéria seca foliar, que é o principal componente forrageiro das espécies, foi maior em C. velutina (3,7 kg ha-1), vindo em seguida A. herbert-smithii (2,8 kg ha-1) e C. coriaria (2,2 kg ha-1), L. diversifolia (2,0 kg ha-1) e M. tenuiflora (1,3 kg ha-1), representando, respectivamente, 7,2; 10,7; 9,5; 5,3; e 6,3% da biomassa total. C. velutina destacou-se por ser a mais produtiva, tanto como madeireira (lenho=30,8 t ha-1) quanto forrageira (folhas = 3,7 t ha-1), enquanto a M. tenuiflora foi a de menor potencial forrageiro
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