1,721,052 research outputs found
Logarithmic divergence of the block entanglement entropy for the ferromagnetic Heisenberg model
No full textRecent studies have shown that logarithmic divergence of entanglement entropy as a function of the size of
a subsystem is a signature of criticality in quantum models. We demonstrate that the ground-state entanglement
entropy of n sites for the ferromagnetic Heisenberg spin- 1/2 chain of the length L in a sector with fixed magnetization y per site grows as 1/2log2fnsL−nd /LgCsyd, where Csyd=2pes14 −y2d
Scaling of the von Neumann entropy across afinite-temperature phase transition
No full textThe spectrum of the reduced density matrix and the temperature
dependence of the von Neumann entropy (VNE) are analytically obtained for a system of hard-core bosons on a complete graph
which exhibits a phase transition to a Bose-Einstein condensate at T = Tc. It is demonstrated that the VNE undergoes a crossover
from purely logarithmic at T = 0 to purely linear in block size
n behaviour for T Tc. For intermediate temperatures,
VNE is a sum of two contributions which are interpreted as the classical (Gibbs) and the quantum (due to entanglement) parts of
the von Neumann entropy
Hydrodynamic limit of multichain driven diffusive models
No full textA class of models, generalizing asymmetric exclusion process for many parallel interacting channels, is
proposed. We couple the models with boundary reservoirs, study boundary-driven phase transitions, and show
that usually taken hydrodynamic description fails. The adequate hydrodynamic limit is then derived. We
support our findings with Monte Carlo simulations of the original stochastic system
Asymmetric simple exclusion process with periodic boundary driving
Get PDFWe consider the asymmetric simple exclusion process (ASEP) on a semi-infinite chain which is coupled at the end to a reservoir with a particle density that changes periodically in time. It is shown that the density profile assumes a time-periodic sawtoothlike shape. This shape does not depend on initial conditions and is found analytically in the hydrodynamic limit. In a finite system, the stationary state is shown to be governed by effective boundary densities and the extremal flux principle. Effective boundary densities are determined numerically via Monte Carlo simulations and compared with those given by mean-field approach and numerical integration of the hydrodynamic limit equation which is the Burgers equation. Our results extend straightforwardly beyond the ASEP to a wide class of driven diffusive systems with one conserved particle species
Entangling power of permutation invariant quantum states
Get PDFWe investigate the von Neumann entanglement entropy as function of the size of a subsystem for permutation invariant ground states in models with finite number of states per site, e.g., in quantum spin models. We demonstrate that the entanglement entropy of n sites in a system of length L generically grows as sigma log(2)[2 pi en(L-n)/L]+C, where sigma is the on-site spin and C is a function depending only on magnetization
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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