1,721,550 research outputs found
On stochastic Langevin and Fokker-Planck equations: The two-dimensional case
Full text linkWe prove existence, regularity in Hölder classes and estimates from above and below of the fundamental solution of the stochastic Langevin equation that is a degenerate SPDE satisfying the weak Hörmander condition. This problem naturally appears in stochastic filtering theory. We use a Wentzell's transform to reduce the SPDE to a PDE with random coefficients. After introducing an original notion of intrinsic solution, we apply a new method based on the parametrix technique to construct it. This approach avoids the use of the Duhamel's principle for the SPDE and the related measurability issues that appear in the stochastic framework. Our results are new even for the deterministic equation in that we prove existence and gradient estimates for the fundamental solution of equations whose coefficients are merely measurable with respect to the time variable. We also propose a different, possibly simpler proof for the Gaussian lower bound
Backward and forward filtering under the weak Hörmander condition
Full text linkWe derive the forward and backward filtering equations for a class of degenerate partially observable diffusions, satisfying the weak Hörmander condition. Our approach is based on the Hölder theory for degenerate SPDEs that allows to pursue the direct approaches proposed by Krylov and Zatezalo, and Veretennikov, avoiding the use of general results from filtering theory. As a by-product we also provide existence, regularity and estimates for the filtering density
The parametrix method for parabolic SPDEs
Full text linkWe consider the Cauchy problem for a linear stochastic partial differential equation. By extending the parametrix method for PDEs whose coefficients are only measurable with respect to the time variable, we prove existence, regularity in Hölder classes and estimates from above and below of the fundamental solution. This result is applied to SPDEs by means of the Itô–Wentzell formula, through a random change of variables which transforms the SPDE into a PDE with random coefficients
47. Piatto da pesce a figure rosse apulo
No full textscheda di piatto da pesce a figure rosse apulo conservato al Museo di Taranto e presentato in mostr
Letter to the Editor: Use of Direct Liver Stiffness Measurement in Evaluating the Severity of Liver Cirrhosis in Patients with Hepatocellular Carcinoma
No full textThe Authors raise some interesting points regarding the effective role of direct liver stiffness measurement in evaluating the severity of liver cirrhosis in patients with HCC undergone surgical resection addressed in the article by Gu et al
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
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