3,356 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
Multipartite Entanglement Signature Of Quantum Phase Transitions.
We derive a general relation between the nonanalyticities of the ground state energy and those of a subclass of the multipartite generalized global entanglement (GGE) measure defined by 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.9717040
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
Fibrosing Alopecia in a Pattern Distribution: Pathogenesis, Diagnosis and Treatment
Fibrosing alopecia in a pattern distribution is a recently recognized type of scarring alopecia, with hair loss in androgens- dependent area. Loss of follicular openings, perifollicular erythema, perifollicular hyperkeratosis and anisotriquia are the trichoscopic clues and follicular lichenoid inflammatory infiltrate the important finding in histopathology. It shares features of androgenetic alopecia and lichen planopilaris. Dermatologists should be familiarized with this entity in order to optimize the diagnosis and provide early treatment to prevent irreversible follicular damage.Alopecia fibrosante em padrão de distribuição androgenética é uma forma clínica de alopecia cicatricial recentemente reconhecida, manifestando-se por rarefacção de cabelo na área dependente de androgénios. Ausência de orifícios foliculares, eritema e hiperqueratose peri-pilar, e anisotriquia são as pistas em tricoscopia e o infiltrado inflamatório liquenóide folicular achado importante em histopatologia. Partilha características de alopecia androgenética e líquen plano pilar. Os dermatologistas devem estar familiarizados com esta entidade, a fim de otimizar o diagnóstico e tratar precocemente, evitando dano folicular irreversível
Symmetry breaking effects upon bipartite and multipartite entanglement in the XY model
We analyze the bipartite and multipartite entanglement for the ground state
of the one-dimensional XY model in a transverse magnetic field in the
thermodynamical limit. We explicitly take into account the spontaneous symmetry
breaking in order to explore the relation between entanglement and quantum
phase transitions. As a result we show that while both bipartite and
multipartite entanglement can be enhanced by spontaneous symmetry breaking deep
into the ferromagnetic phase, only the latter is affected by it in the vicinity
of the critical point. This result adds to the evidence that multipartite, and
not bipartite, entanglement is the fundamental indicator of long range
correlations in quantum phase transitions.Comment: 13 pages, 19 figures, comments welcome. V2: small changes, published
versio
Complete State Reconstruction of a Two-Mode Gaussian State via Local Operations and Classical Communication
We propose a strictly local quantum tomography protocol for a bipartite
system. We show that the joint density matrix of an arbitrary two-mode Gaussian
state, entangled or not, is obtained via local operations and classical
communication only. In contrast to previous proposals, simultaneous homodyne
measurements (HM) on both modes are replaced by local homodyne detections and a
set of local projective measurements.Comment: 4 pages, 1 figure, double column RevTex4; v2: presentation improved,
references update
Dissolving star cluster candidates
We present a list of 34 neglected entries from star cluster catalogues
located at relatively high galactic latitudes ( 15) which
appear to be candidate late stages of star cluster dynamical evolution.
Although underpopulated with respect to usual open clusters, they still present
a high number density contrast as compared to the galactic field. This was
verified by means of (i) predicted model counts from different galactic
subsystems in the same direction, and (ii) Guide Star Catalog equal solid angle
counts for the object and surrounding fields. This suggests that the objects
are physical systems, possibly star clusters in the process of disruption or
their fossil remains. The sample will be useful for followup studies in view of
verifying their physi cal nature.Comment: manuscript in LATEX with 7 pages, 7 figures .ps Accepted for
Astronomy and Astrophysics main journa
Chemical composition and minerals in pyrite ash of an abandoned sulphuric acid production plant
The extraction of sulphur produces a hematite-rich waste, known as roasted pyrite ash, which contains significant amounts of environmentally sensitive elements in variable concentrations and modes of occurrence. Whilst the mineralogy of roasted pyrite ash associated with iron or copper mining has been studied, as this is the main source of sulphur worldwide, the mineralogy, and more importantly, the characterization of submicron, ultrafine and nanoparticles, in coal-derived roasted pyrite ash remain to be resolved. In this work we provide essential data on the chemical composition and nanomineralogical assemblage of roasted pyrite ash. XRD, HR-TEM and FE-SEM were used to identify a large variety of minerals of anthropogenic origin. These phases result from highly complex chemical reactions occurring during the processing of coal pyrite of southern Brazil for sulphur extraction and further manufacture of sulphuric acid. Iron-rich submicron, ultrafine and nanoparticles within the ash may contain high proportions of toxic elements such as As, Se, U, among others. A number of elements, such as As, Cr, Cu, Co, La, Mn, Ni, Pb, Sb, Se, Sr, Ti, Zn, and Zr, were found to be present in individual nanoparticles and submicron, ultrafine and nanominerals (e.g. oxides, sulphates, clays) in concentrations of up to 5%. The study of nanominerals in roasted pyrite ash from coal rejects is important to develop an understanding on the nature of this by-product, and to assess the interaction between emitted nanominerals, ultra-fine particles, and atmospheric gases, rain or body fluids, and thus to evaluate the environmental and health impacts of pyrite ash materials
O CONHECIMENTO MATEMÁTICO SOBRE OS DESCRITORES “ESPAÇO E FORMA” DE LICENCIANDOS EM UM CURSO DE PEDAGOGIA NA MODALIDADE A DISTÂNCIA: RESULTADOS PARCIAIS
Neste artigo, apresentam-se os conteúdos matemáticos abordados na Prova Brasil no 5º ano do Ensino Fundamental, em relação ao Tema I - Espaço e Forma, da matriz de referência, analisados em trêsatividades propostas a 47 licenciandos de um curso de Pedagogia na modalidade à distância, distribuídos em 6 polos de diferentes cidades da Universidade Aberta do Brasil. Por meio das atividades resolvidas pelos licenciandos, evidenciam-se as dificuldades dos alunos quanto à identificação das figuras tridimensionais, dos polígonos e quadriláteros e suas propriedades e as relações entre seus lados (paralelos, congruentes, perpendiculares). Desse estudo, concluiu-se que os materiais disponibilizados no Ambiente Virtual de Aprendizagem da disciplina “Espaço e Forma” não se referenciaram nos descritores de matemática na elaboração de sua ementa. Tal ação pedagógica poderia ter contribuído para a construção e organização dos conhecimentos matemáticos doslicenciandos em relação ao Tema I
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