1,720,997 research outputs found
Unitary representations of super groups and Mackey theory
No full textWe outline some basic facts in the theory of unitary representations of super Lie groups along the lines of [C. Carmeli, G. Cassinelli, A. Toigo, and V.S. Varadarajan. "Unitary representations of super lie groups and applications to the classification and multiplet structure of super particles", Comm. Math. Phys. 263 (2006) 217-258]. We define the concept of representation induced from a special sub super group. We give a version of Mackey theory for groups containing a special normal abelian connected sub super group
On the coexistence of position and momentum observables
No full textWe investigate the problem of coexistence of position and momentum observables. We characterize those pairs of position and momentum observables which have a joint observable
Intrinsic unsharpness and approximate repeatability of quantum measurements
No full textThe intrinsic unsharpness of a quantum observable is studied by introducing the notion of resolution width. This quantification of accuracy is shown to be closely connected with the possibility of making approximately repeatable measurements. As a case study, the intrinsic unsharpness and approximate repeatability of position and momentum measurements are examined in detail
Minimal covariant observables identifying all pure states
No full textIt has been recently shown by Heinosaari, Mazzarella and Wolf (2013) [1] that an observable that identifies all pure states of a d-dimensional quantum system has minimally 4d - 4 outcomes or slightly less (the exact number depending on d). However, no simple construction of this type of minimal observable is known. We investigate covariant observables that identify all pure states and have minimal number of outcomes. It is shown that the existence of this kind of observables depends on the dimension of the Hilbert space
Why unsharp observables?
No full textWe discuss why projection valued measures are not sufficient in the description of position and momentum of a one dimensional particle. A satisfactory solution is offered using positive operator measures. We also argue why the relevant positive operator measures, but not all, may be called unsharp observables
Super Distributions, Analytic and Algebraic Super Harish-Chandra pairs
No full textWe extend the theory of super Harish-Chandra pairs, originally developed by Kostant
and Koszul for smooth Lie supergroups, to algebraic supergroups over a field of
characteristic zero. We also review the corresponding complex analytic theory
and we give a characterization of the action of an algebraic (resp. complex
analytic) super Harish-Chandra pair on a supervariety (resp. complex analytic
supermanifold)
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
Sequential measurements of conjugate observables
No full textWe present a unified treatment of sequential measurements of two conjugate observables. Our approach is to derive a mathematical structure theorem for all the relevant covariant instruments. As a consequence of this result, we show that every Weyl–Heisenberg covariant observable can be implemented as a sequential measurement of two conjugate observables. This method is applicable both in finite- and infinite-dimensional Hilbert spaces, therefore covering sequential spin component measurements as well as position-momentum sequential measurements
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