1,721,870 research outputs found
Regularization of the Hamiltonian constraint compatible with the spinfoam dynamics
No full textWe introduce a new regularization for Thiemann's Hamiltonian constraint. The resulting constraint can generate the 1-4 Pachner moves and is therefore more compatible with the dynamics defined by the spinfoam formalism. We calculate its matrix elements and observe the appearance of the 15j Wigner symbol in these
Statistical mechanics of reparametrization-invariant systems. It takes three to tango
No full textIt is notoriously difficult to apply statistical mechanics to generally covariant systems, because the notions of time, energy, and equilibrium are seriously modified in this context. We discuss the conditions under which weaker versions of these notions can be defined, sufficient for statistical mechanics. We focus on reparametrization-invariant systems without additional gauges. The key is to reconstruct statistical mechanics from the ergodic theorem. We find that a suitable split of the system into two non interacting components is sufficient for generalizing statistical mechanics. While equilibrium acquires sense only when the system admits a suitable split into three weakly interacting components - roughly: a clock and two systems among which a generalization of energy is equi-partitioned. This allows the application of statistical mechanics and thermodynamics as an additivity condition of such generalized energy
Physics with nonperturbative quantum gravity: radiation from quantum black holes
No full textQuesto lavoro
e' risultato vincitore del II premio della
Gravity Research Foundation per il 199
Coupling and thermal equilibrium in general-covariant systems
No full textA fully general-covariant formulation of statistical mechanics is still lacking. We take a step toward this theory by studying the meaning of statistical equilibrium for coupled, parametrized systems. We discuss how to couple parametrized systems. We express the thermalization hypothesis in a general-covariant context. This takes the form of vanishing of information flux. An interesting relation emerges between thermal equilibrium and gauge. © 2013 American Physical Society
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Spacetime thermodynamics without hidden degrees of freedom
No full textA celebrated result by Jacobson is the derivation of Einstein's equations from Unruh's temperature, the Bekenstein-Hawking entropy and the Clausius relation. This has been repeatedly taken as evidence for an interpretation of Einstein's equations as equations of state for unknown degrees of freedom underlying the metric. We show that a different interpretation of Jacobson's result is possible, which does not imply the existence of additional degrees of freedom, and follows only from the quantum properties of gravity. We introduce the notion of quantum gravitational Hadamard states, which give rise to the full local thermodynamics of gravity. © 2014 American Physical Society
Prevention and treatment of recurrent cellulitis
No full textPurpose of reviewRecurrent cellulitis is a challenging clinical condition affecting up to 47% of patients after the first episode, especially those with predisposing risk factors. The purpose of this review is to describe the state of the art of literature evidence and to highlight recent developments in its management.Recent findingsRecurrent cellulitis can occur after successful treatment of cellulitis. Conditions that commonly increase the risk of cellulitis include local and systemic modifiable and nonmodifiable factors. A rigorous approach to the management of risk factors and treatment of acute infection is important as the risk of recurrence rises with repeated episodes. Risk factors, if present, need to be targeted in association with antibiotic prophylaxis. Penicillin V is the preferred antibiotic for prevention but other antibiotics and new drugs can be considered in cases of beta-lactam allergy, intolerance, or failure.Recurrent cellulitis is associated with short term and long-term morbidity as well as significant healthcare costs. Management of underlying predisposing conditions is crucial to prevent recurrence in addition with evaluation of pharmacological measures, but specialized and multidisciplinary skills are needed. More efforts are needed to prevent and treat this underestimated problem
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