1,721,022 research outputs found
Dispersion Estimates for Spherical Schrödinger Equations
Get PDFWe derive a dispersion estimate for one-dimensional perturbed radial Schrödinger operators. We also derive several new estimates for solutions of the underlying differential equation and investigate the behavior of the Jost function near the edge of the continuous spectrum.Fil: Kostenko, Aleksey. Universidad de Viena; AustriaFil: Teschl, Gerald. Universidad de Viena; AustriaFil: Toloza, Julio Hugo. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación en Informática para la Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Singular Schrödinger operators as self-adjoint extensions of N-entire operators
Get PDFWe investigate the connections between Weyl–Titchmarsh– Kodaira theory for one-dimensional Schrödinger operators and the theory of n-entire operators. As our main result we find a necessary and sufficient condition for a one-dimensional Schrödinger operator to be n-entire in terms of square integrability of derivatives (w.r.t. the spectral parameter) of the Weyl solution. We also show that this is equivalent to the Weyl function being in a generalized Herglotz–Nevanlinna class. As an application we show that perturbed Bessel operators are n-entire, improving the previously known conditions on the perturbation.Fil: Silva, Luis O.. Universidad Nacional Autónoma de México; MéxicoFil: Teschl, Gerald. Universidad de Viena; AustriaFil: Toloza, Julio Hugo. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación en Informática para la Ingeniería; Argentin
Asymptotic behavior of the Weyl m-function for one-dimensional Schrödinger operators with measure-valued potentials
Get PDFWir betrachten die Sturm-Liouville Differentialgleichung mit maßwertigen Koeffizienten und führen die Weyl m-Funktion für selbstadjungierte Realisierungen ein. Weiters betrachten wir den Spezialfall der eindimensionalen Schrödinger Operatoren mit maßwertigen Potentialen. Für diesen Fall entwickeln wir eine verbesserte Abschätzung der Hochenergieasymptotik für die Weyl m-Funktion.We consider the Sturm-Liouville differential expression with measure-valued coefficients and introduce the Weyl m-function for self-adjoint realizations. We further look at the special case of one-dimensional Schrödinger operators with measure-valued potentials. For this case we develop an improved estimate for the high energy asymptotics of the Weyl m-function
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
Some spectral properties of Rooms and Passages domains and their skeletons
No full textIn this paper we investigate spectral properties of Laplacians on Rooms and Passages domains. In the first part, we use Dirichlet-Neumann bracketing techniques to show that for the Neumann Laplacian in certain Rooms and Passages domains the second term of the asymptotic expansion of the counting function is of order . For the Dirichlet Laplacian our methods only give an upper estimate of the form . In the second part of the paper, we consider the relationship between Neumann Laplacians on Rooms and Passages domains and Sturm-Liouville operators on the skeleton
Finite gap Jacobi matrices: A review
Get PDFPerhaps the most common theme in Fritz Gesztesy's broad opus is the study of problems with periodic or almost periodic finite gap differential and difference equations, especially those connected to integrable systems. The present paper reviews recent progress in the understanding of finite gap Jacobi matrices and their perturbations. We'd like to acknowledge our debt to Fritz as a collaborator and
friend. We hope Fritz enjoys this birthday bouquet
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