20,805 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
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
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
Operational Classification and Quantification of Multipartite Entangled States
We formalize and extend an operational multipartite entanglement measure
introduced by T. R. Oliveira, G. Rigolin, and M. C. de Oliveira, Phys. Rev. A
73, 010305(R) (2006), through the generalization of global entanglement (GE)
[D. A. Meyer and N. R. Wallach, J. Math. Phys. 43, 4273 (2002)]. Contrarily to
GE the main feature of this measure lies in the fact that we study the mean
linear entropy of all possible partitions of a multipartite system. This allows
the construction of an operational multipartite entanglement measure which is
able to distinguish among different multipartite entangled states that GE
failed to discriminate. Furthermore, it is also maximum at the critical point
of the Ising chain in a transverse magnetic field, being thus able to detect a
quantum phase transition.Comment: 14 pages, RevTex4, published versio
Agência de Informação Embrapa: uma ferramenta para gestão do conhecimento em empresas de PD&I.
O conhecimento é o maior bem intangível das empresas e deve-se buscar a melhor maneira de geri-lo. Para fortalecer a gestão do conhecimento no âmbito agropecuário, a Empresa Brasileira de Pesquisa Agropecuária (Embrapa) desenvolveu o projeto Agência de Informação Embrapa, para organizar e tornar acessível o conhecimento gerado pela Empresa desde 1973. Essa ferramenta facilita o acesso à informação, através de um sistema web rápido e seguro. A informação disponível para consulta é validada por uma equipe técnica composta por especialistas em diversos temas do domínio agropecuário. O objetivo desse trabalho é mostrar que a Agência de Informação Embrapa é uma ferramenta adequada a outras Instituições de PD&I. Para alcançá-lo, alguns fatores que motivam e dão continuidade a um sistema de suporte à decisão foram analisados, além de indicadores que identificam o sucesso da gestão do conhecimento nas empresas. O estudo de caso foi realizado na Embrapa Informática Agropecuária, uma das unidades de pesquisa responsáveis pelo projeto. Os resultados deste estudo demonstraram que a Agência contempla requisitos, tanto do ponto de vista da tecnologia da informação, como da gestão do conhecimento, para orientar novas pesquisas e auxiliar a tomada de decisão em Empresas de PD&I.CISCI 2009
Glassy behaviour in short range lattice models without quenched disorder
We investigate the quenching process in lattice systems with short range
interaction and several crystalline states as ground states. We consider in
particular the following systems on square lattice:
- hard particle (exclusion) model;
- q states planar Potts model.
The system is initially in a homogeneous disordered phase and relaxes toward
a new equilibrium state as soon as the temperature is rapidly lowered. The time
evolution can be described numerically by a stochastic process such as the
Metropolis algorithm. The number of pure, equivalent, ground states is q for
the Potts model and r for the hard particle model, and it is known that for r
or q larger or equal to d+1, the final equilibrium state may be
polycrystalline, i.e. not made of a uniform phase. We find that in addition n_g
and q_g exist such that for r > r_g, or q > q_g the system evolves toward a
glassy state, i.e. a state in which the ratio of the interaction energy among
the different crystalline phases to the total energy of the system never
vanishes; moreover we find indications that r_g=q_g. We infer that q=q_g (and
r=r_g) corresponds to the crossing from second order to discontinuous
transition in the phase diagram of the system.Comment: 10 pages, 3 figure
Characterization of the second- and third-order nonlinear optical susceptibilities of monolayer MoS using multiphoton microscopy
We report second- and third-harmonic generation in monolayer MoS
as a tool for imaging and accurately characterizing the material's nonlinear
optical properties under 1560 nm excitation. Using a surface nonlinear optics
treatment, we derive expressions relating experimental measurements to second-
and third-order nonlinear sheet susceptibility magnitudes, obtaining values of
m V and for the first time for
monolayer MoS, m V.
These sheet susceptibilities correspond to effective bulk nonlinear
susceptibility values of m V and
m V, accounting for the sheet
thickness. Experimental comparisons between MoS and graphene are
also performed, demonstrating 3.4 times stronger third-order sheet
nonlinearity in monolayer MoS, highlighting the material's
potential for nonlinear photonics in the telecommunications C band.Comment: Accepted by 2D Materials, 28th Oct 201
The mathematical description of the electrosynthesis of composites of oxy-hydroxycompounds cobalt with polypyrrole overooxidazed
The electrosynthesis of the composite with of the overoxidized polypyrrole with cobalt oxy-hydroxide in strongly acidic media has been described mathematically, using linear stability theory and bifurcation analysis. The steadystates stability conditions and oscillatory and monotonic instability requirements have been described too. The system´s behavior was compared with behavior of other systems with overoxidation, electropolymerization of heterocyclic compounds and electrosynthesis of the cobalt oxy-hydroxides
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