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: $GHZ_{N}$, $W_{N}$, and $EPR^{\otimes N/2}$. 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

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

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

Evaluation of the Interest in the Academic Career of Physicians Specializing in Anesthesiology

SummaryBackground and objectivesA trend toward the lack of interest in academic careers has been observed in Medicine, including in the area of Anesthesiology. The objective of the present study was to research the interest of physicians specializing in Anesthesiology in following an academic career, as well as identify the determinant factors of this choice.MethodThe present was a prospective and cross-sectional study. A simple probabilistic sample of physicians specializing in Anesthesiology was selected and a questionnaire was sent to each participant. The answers were submitted to uni and multivariate analyses to determine the frequency of academic predisposition in the sample and to determine the independent predictive factors of academic predisposition.ResultsA total of 155 questionnaires were analyzed (rate of response = 38.7%). Sixty-nine participants (44.5%) manifested their interest in following an academic career. The multivariate analysis identified the following as independent predictive factors of academic predisposition: attending the first year of specialization (OR = 2.52; 95% CI = 1.19 – 5.38); presenting a scientific work at medical event (OR = 3.78; 95% CI = 1.84 – 7.78) and being located in the southeast region (OR = 2.66; 95% CI = 1.31 – 5.39).ConclusionsA significant number of Brazilian physicians attending a specialization course demonstrated interest in following an academic career after the end of the course. In comparison with the probability of not manifesting academic predisposition, the physicians attending the first-year specialization course presented a 2.5-fold higher chance of manifesting interest in an academic career; those presenting a scientific work at a medical event had a 3.78-fold higher chance; those associated to Teaching Centers in the southeast region had a 2.66-fold higher chance of manifesting academic interest

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

Impact of short-term water exercise programs on weight, body composition, metabolic profile and quality of life of obese women

Physical exercises performed in water, such as water aerobics, have a minimal impact on the joints and are frequently indicated to help obese individuals to lose weight. The objective of this study was to compare the effects of two water programs (continuous vs intermittent) on the body composition, resting energy expenditure (REE), metabolic profile, and quality of life of obese women without nutritional intervention. Twenty-seven sedentary female volunteers (mean age and BMI of 42.8±7.4 years and 36.1±6.3kg.m-2, respectively) were selected and allocated randomly into two groups: continuous water exercise (CON) and intermittent water exercise (INT). Both programs lasted two months with 3 weekly sessions of 60 minutes each. The following evaluations were performed before and after the intervention: anthropometry (weight and body circumferences), body composition (fat mass and fat-free mass), metabolic profile (glycemia and lipid profile), REE (indirect calorimetry), and quality of life (SF-36 Questionnaire).Comparisons between groups and times (initial and final) were performed using the nonparametric Wilcoxon test. The groups did not differ in any of the variables analyzed at the initial time (Ti) and at the final time (Tf). Comparison of Ti vs f revealed significant reductions of weight (-0.6 kg), BMI(-0.3 kg.m-2), fat mass (-0.6 kg), arm circumference (-1.8cm) and hip circumference (-4.0cm) for CON group and significant reductions of only fat mass (-0.6kg)and arm circumference (-2.0cm) for INT group. Regarding quality of life, improvement in social and vitality aspects was observed in CON group and improvement in vitality and health status in INT group. Short-term water exercise programs not associated with nutritional monitoring have a modest impact on the weight, body composition and metabolic profile of obese women, with better results for programs with continuous characteristics. However, the improvement of quality of life aspects should not be overlooked

Evolutionary processes underlying latitudinal differences in reef fish biodiversity

Aim: To examine the dynamics among the processes of speciation, extinction and dispersal in marine environments using phylogenies to reveal the evolutionary mechanisms that promote latitudinal differences in biodiversity. Using phylogenetic comparative methods we assess whether tropical reef fish lineages show higher diversification rates and whether the majority of extratropical reef fish lineages have originated from tropical areas. Location: Shallow water tropical and extratropical reefs globally. Methods: Using fossil-calibrated phylogenies for four reef-associated fish families (Chaetodontidae, Labridae, Pomacentridae and Sparidae) we apply evolutionary models (GeoSSE and HiSSE) that allow the estimation of speciation, extinction and dispersal rates associated with geographical ranges and explore potential biases from unsampled characters. Results: We found that tropical lineages show higher rates of speciation and tended to have lower extinction rates. Overall, we identify higher net diversification rates for tropical lineages compared with those in extratropical regions in all four families. Rates of dispersal tended to be higher for lineages with tropical origins expanding into extratropical regions. Within the family Labridae, two tropical lineages were found to exhibit higher net diversification rates, above that expected from latitudinal differences. Main conclusions : Our results offer support for the predictions of the out of the tropics' and evolutionary speed' models of evolution, both of which highlight the marine tropics as an important evolutionary engine promoting latitudinal differences in reef fish biodiversity. Moreover, we find that two tropical labrid lineages are undergoing exceptional diversification associated with additional traits, possibly linked with the extreme sexual dichromatism observed in both clades