1,720,963 research outputs found
Novel phases in long-range many-body systems
Get PDFMany-body systems with long-range power-law decaying potentials among their microscopic components are known to fall outside the traditional framework of complex systems. While some peculiarities in their behavior had emerged since the
very early days of statistical mechanics, the possibility of engineering such systems
in experimental setups based on molecular and optical systems has stimulated an im-
pressive theoretical activity in the last decades, unveiling a plethora of new physical
phenomena. In particular, depending on the exact form of the couplings, long-range-
interacting systems may avoid thermalization, remaining trapped in long-lived metastable phases, or exhibit new equilibrium phases at thermal equilibrium. The study of such novel phases, emerging both in the equilibrium behavior and in the dynamics, is the subject of the present thesis. In particular, in Part I the equilibrium behavior of long-range XY model and long-range Villain model are studied, while in the second part the quantum dynamics of long-range spin chains, both isolated and subjected to periodic driving, is investigated
Villain model with long-range couplings
Get PDFThe nearest-neighbor Villain, or periodic Gaussian, model is a useful tool to
understand the physics of the topological defects of the two-dimensional
nearest-neighbor model, as the two models share the same symmetries and
are in the same universality class. The long-range counterpart of the
two-dimensional model has been recently shown to exhibit a non-trivial
critical behavior, with a complex phase diagram including a range of values of
the power-law exponent of the couplings decay, , in which there are a
magnetized, a disordered and a critical phase (arXiv:2104.13217). Here we
address the issue of whether the critical behavior of the two-dimensional
model with long-range couplings can be described by the Villain counterpart of
the model. After introducing a suitable generalization of the Villain model
with long-range couplings, we derive a set of renormalization-group equations
for the vortex-vortex potential, which differs from the one of the long-range
model, signaling that the decoupling of spin-waves and topological defects
is no longer justified in this regime. The main results are that for
the two models no longer share the same universality class. Remarkably, within
a large region of its phase diagram, the Villain model is found to behave
similarly to the one-dimensional Ising model with interactions.Comment: 13+7 pages, 2+1 figure
Quantum heat engine with long-range advantages
Get PDFLong-range interacting quantum devices provides a promising route for quantum technology applications. Here, the presence of long-range interactions is shown to enhance the performances of a quantum heat engine featuring a many-body working substance. We focus on the paradigmatic example of a Kitaev chain undergoing a quantum Otto cycle and show that a substantial thermodynamic advantage may be achieved as the range of the interactions among its constituents increases. The advantage is most significant for the realistic situation of a finite time cycle: the presence of long-range interactions reduces the non-adiabatic energy losses, by suppressing the detrimental effects of dynamically generated excitations. This effect allows mitigating the trade-off between power and efficiency, paving the way for a wide range of experimental and technological applications
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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