1,724,965 research outputs found
Gauge groups and bialgebroids
Full text linkWe study the Ehresmann–Schauenburg bialgebroid of a noncommutative principal bundle as a quantization of the gauge groupoid of a classical principal bundle. We show that the gauge group of the noncommutative bundle is isomorphic to the group of bisections of the bialgebroid, and we give a crossed module structure for the bisections and the automorphisms of the bialgebroid. Examples include: Galois objects of Taft algebras, a monopole bundle over a quantum sphere and a not faithfully flat Hopf–Galois extension of commutative algebras. For each of the latter two examples, there is in fact a suitable invertible antipode for the bialgebroid making it a Hopf algebroid
Non-topological Vortex Configurations in the ABJM Model
No full textIn this paper we study the existence of vortex-type solutions for a system of self-dual equations deduced from the mass-deformed Aharony–Bergman–Jafferis–Maldacena (ABJM) model. The governing equations, derived by Mohammed, Murugan, and Nastse under suitable ansatz involving fuzzy sphere matrices, have the new feature that they can support only non-topological vortex solutions. After transforming the self-dual equations into a nonlinear elliptic 2×2 system we prove first an existence result by means of a perturbation argument based on a new and appropriate scaling for the solutions. Subsequently, we prove a more complete existence result by using a dynamical analysis together with a blow-up argument. In this way we establish that any positive energy level is attained by a 1-parameter family of vortex solutions, which also correspond to (constraint) energy minimizers. In other words, we register the exceptional fact in a BPS-setting that, neither a “quantization” effect nor an energy gap is induced upon the system by the rigid “critical” coupling of the self-dual regime
Multiple solutions for the non-Abelian Chern–Simons–Higgs vortex equations
No full textIn this paper we study the existence of multiple solutions for the non-Abelian Chem-Simons-Higgs (N x N)-system:Delta u(i) = lambda(Sigma(N)(j=1) Sigma(N)(k=1) K(kj)K(ji)e(uj)e(uk) - Sigma(N)(j=1) k(ji)e(uj)) + 4 pi Sigma(ni)(j=1) delta(pij), i=1, . . . , N;over a doubly periodic domain Omega, with coupling matrix K given by the Cartan matrix of SU(N + 1), (see (1.2) below). Here, lambda > 0 is the coupling parameter, delta(p )is the Dirac measure with pole at p and n(i) is an element of N, for i = 1,...,N. When N = 1, 2 many results are now available for the periodic solvability of such system and provide the existence of different classes of solutions known as: topological, non-topological, mixed and blow-up type. On the contrary for N >= 3, only recently in [27] the authors managed to obtain the existence of one doubly periodic solution via a minimization procedure, in the spirit of [46]. Our main contribution in this paper is to show (as in [46]) that actually the given system admits a second doubly periodic solutions of "Mountain-pass" type, provided that 3 <= N <= 5. Note that the existence of multiple solutions is relevant from the physical point of view. Indeed, it implies the co-existence of different non-Abelian Chem-Simons condensates sharing the same set (assigned component-wise) of vortex points, energy and fluxes. The main difficulty to overcome is to attain a "compactness" property encompassed by the so-called Palais-Smale condition for the corresponding "action" functional, whose validity remains still open for N >= 6. (C) 2019 Elsevier Masson SAS. All rights reserved
Liquid-to-glass transition in bulk glass-forming Cu60Ti20Zr20 alloy by molecular dynamics simulations
No full textWe report results from molecular dynamics studies concerning the microscopic structure and dynamics of the ternary, bulk metallic glass-forming Cu60Ti20Zr20 alloy. In detail we consider the partial radial distribution functions, nearest-neighbor numbers, specific heat, simulated glass temperature, diffusion coefficients, and incoherent intermediate scattering function (ISF). The applied atomic model reproduces well experimental x-ray data of the total radial distribution function. It provides for Cu60Ti20Zr20 a structure with marked intermediate-range order. The ISF is analyzed within an extension of mode-coupling theory, where the effective memory kernel is evaluated from the Laplace transform of the ISF. The dynamics of the system fulfills in most respects the predictions of mode-coupling theory (MCT), up to an absence of the algebraic t(-a) decay in the early beta range. Comparison with the calculated memory kernel shows that this absence can be traced back to deviations of the kernel from its approximate form analyzed in MCT. As by-product, our investigation provides a method to reconstruct around the critical temperature major parts of the memory kernel from lambda and the plateau value f(c) of the ISF, and it indicates why the critical dynamics predicted by mode-coupling theory can be observed in a temperature interval of more than 500 K
Doubly periodic self-dual vortices in a relativistic non-Abelian Chern–Simons model
No full textIn this paper we establish a multiplicity result concerning the existence of doubly periodic solutions in a 2 × 2 nonlinear elliptic system arising in the study of self-dual non-Abelian Chern-Simons vortices. We show that the system admits at least two solutions when the Chern-Simons coupling parameter ? >0 sufficiently large. As in Nolasco and Tarantello (Commun Math Phys 213:599-639, 2000), we use a variational formulation of the problem. Thus, we obtain a first solution via a constrained minimization method and show that it is asymptotically gauge-equivalent to the (broken) principal embedding vacuum of the system, as ? ? 0. Then we obtain a second solution by a min-max procedure of "mountain pass" type
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
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