2,191 research outputs found
The Glue Around Quarks and the Interquark Potential
The quarks of quark models cannot be identified with the quarks of the QCD
Lagrangian. We review the restrictions that gauge field theories place on any
description of physical (colour) charges. A method to construct charged
particles is presented. The solutions are applied to a variety of applications.
Their Green's functions are shown to be free of infra-red divergences to all
orders in perturbation theory. The interquark potential is analysed and it is
shown that the interaction responsible for anti-screening results from the
force between two separately gauge invariant constituent quarks. A fundamental
limit on the applicability of quark models is identified.Comment: 4 pages, LaTeX, talk given at Montpellier meeting QCD9
Quantumness in decoherent quantum walk using measurement-induced disturbance
The classicalization of a decoherent discrete-time quantum walk on a line or
an n-cycle can be demonstrated in various ways that do not necessarily provide
a geometry-independent description. For example, the position probability
distribution becomes increasingly Gaussian, with a concomitant fall in the
standard deviation, in the former case, but not in the latter. As another
example, each step of the quantum walk on a line may be subjected to an
arbitrary phase gate, without affecting the position probability distribution,
no matter whether the walk is noiseless or noisy. This symmetry, which is
absent in the case of noiseless cyclic walk, but is restored in the presence of
sufficient noise, serves as an indicator of classicalization, but only in the
cyclic case. Here we show that the degree of quantum correlations between the
coin and position degrees of freedom, quantified by a measure based on the
disturbance induced by local measurements (Luo, Phys. Rev. A 77, 022301
(2008)), provides a suitable measure of classicalization across both type of
walks. Applying this measure to compare the two walks, we find that cyclic
quantum walks tend to classicalize faster than quantum walks on a line because
of more efficient phase randomization due to the self-interference of the two
counter-rotating waves. We model noise as acting on the coin, and given by the
squeezed generalized amplitude damping (SGAD) channel, which generalizes the
generalized amplitude damping channel.Comment: 8 pages with 8 figures, Published versio
Girls and Gangs: A Decade on From the Firmin Report and What Has Changed?
Presenting data from the first phase of a U.K.-based 5-year mixed-methods study, we restart a decade-long conversation into Girls and Gangs and Violence Against Women and Girls (VAWG). The relationship between the two is not mutually exclusive and coupled with the recent optics surrounding youth violence and gendered violence, we discuss how the needs of women are being somewhat hindered as a result of U.K. governmental vacillation. We therefore consider the serious impact of VAWG and the concomitancy with youth violence/gangs. By drawing on contemporary feminist criminological theorizing, we aim to galvanize governmental responses to prioritize the needs of women at a time when policymakers are arguably poised to listen
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