16,282 research outputs found
Bethe--Salpeter equation in QCD
We extend to regular QCD the derivation of a confining
Bethe--Salpeter equation previously given for the simplest model of scalar QCD
in which quarks are treated as spinless particles. We start from the same
assumptions on the Wilson loop integral already adopted in the derivation of a
semirelativistic heavy quark potential. We show that, by standard
approximations, an effective meson squared mass operator can be obtained from
our BS kernel and that, from this, by expansion the
corresponding Wilson loop potential can be reobtained, spin--dependent and
velocity--dependent terms included. We also show that, on the contrary,
neglecting spin--dependent terms, relativistic flux tube model is reproduced.Comment: 23 pages, revte
From scalar to string confinement
We outline a connection between scalar quark confinement, a
phenomenologically successful concept heretofore lacking fundamental
justification, and QCD. Although scalar confinement does not follow from QCD,
there is an interesting and close relationship between them. We develop a
simple model intermediate between scalar confinement and the QCD string for
illustrative purposes. Finally, we find the bound state masses of scalar,
time-component vector, and string confinement analytically through
semi-classical quantization.Comment: ReVTeX, 9 pages, 5 figure
Two phase transitions in the fully frustrated model
The fully frustrated model on a square lattice is studied by means of
Monte Carlo simulations. A Kosterlitz-Thouless transition is found at , followed by an ordinary Ising transition at a slightly
higher temperature, . The non-Ising exponents reported by
others, are explained as a failure of finite size scaling due to the screening
length associated with the nearby Kosterlitz-Thouless transition.Comment: REVTEX file, 8 pages, 5 figures in uuencoded postscrip
Untangling the knot: The information practices of enthusiast car restorers
© 2019 ASIS & T A study of enthusiast car restorers is used to illustrate how an information practice approach can provide information science researchers with a richer, more nuanced understanding of the complex interrelationship between people, technology, and information. An ethnographic approach incorporating both semistructured interviews and in the garage ethnographic observation was employed. Analysis was undertaken using an inductive, thematic approach. The findings demonstrate that participants' information environments are rich and complex. Participants' accounts emphasized the corporeal and embodied nature of the restoration process, and this may account for why they privileged the social networks they had developed, often over many decades, over online resources and communities. The findings indicate that participants are engaged in much more than applied problem solving. What is also evident is that engagement in the social world of car restoration, and the networks of social knowledge sharing it affords, is significant for the emotional support it provides for older men who often lose these networks later in life. In a sense, the participants are not only rebuilding their cars but also their own sense of self
Enacting and capturing embodied knowledge in the practices of enthusiast car restorers: Emerging themes
© The Author(s) 2018. This paper reports on emerging themes drawn from a larger ongoing qualitative study of car restorers which explores themes of embodiment, embodied knowledge and ways of knowing. The themes described in this current article indicate that car restoration is bounded within a discourse of loyalty to the particular type of practice and its projects (restoration), its material object (the car) and to narratives of expertise, maintenance and preservation. The study’s findings also demonstrate that enthusiast car restorers, along with other serious leisure communities, have become the unacknowledged custodians of a large body of hands-on knowledge which would otherwise be in danger of being lost in an increasingly post-industrial world
Analytic Quantization of the QCD String
We perform an analytic semi-classical quantization of the straight QCD string
with one end fixed and a massless quark on the other, in the limits of orbital
and radial dominant motion. We compare our results to the exact numerical
semi-classical quantization. We observe that the numerical semi-classical
quantization agrees well with our exact numerical canonical quantization.Comment: RevTeX, 10 pages, 9 figure
Semileptonic form factors - a model-independent approach
We demonstrate that the B->D(*) l nu form factors can be accurately predicted
given the slope parameter rho^2 of the Isgur-Wise function. Only weak
assumptions, consistent with lattice results, on the wavefunction for the light
degrees of freedom are required to establish this result. We observe that the
QCD and 1/m_Q corrections can be systematically represented by an effective
Isgur-Wise function of shifted slope. This greatly simplifies the analysis of
semileptonic B decay. We also investigate what the available semileptonic data
can tell us about lattice QCD and Heavy Quark Effective Theory. A rigorous
identity relating the form factor slope difference rho_D^2-rho_A1^2 to a
combination of form factor intercepts is found. The identity provides a means
of checking theoretically evaluated intercepts with experiment.Comment: 18 pages, Revtex, 4 postscript figures, uses epsfig.st
Semi-leptonic B decays into higher charmed resonances
We apply HQET to semi-leptonic meson decays into a variety of excited
charm states. Using three realistic meson models with fermionic light degrees
of freedom, we examine the extent that the sum of exclusive single charmed
states account for the inclusive semi-leptonic decay rate. The consistency
of form factors with the Bjorken and Voloshin sum rules is also investigated.Comment: Latex, 27 pages. A few references and errors corrected, to appear in
Phys. Rev.
Polarization observables of the gamma d --> PiNN reaction in the Delta(1232)-resonance region
Polarization observables of the three charge states of the pion for the
reaction with polarized photon beam and/or oriented
deuteron target are evaluated over the whole (1232)-resonance region
adopting a nonrelativistic model based on time-ordered perturbation theory.
Results for the -meson spectra, linear photon asymmetry, vector and tensor
target asymmetries are presented. Particular attention is given, for the first
time, to double polarization asymmetries for which we present results for
and . We found that all other double
polarization asymmetries of photon and deuteron target are vanished.Comment: 17 Pages, 8 Figures, accepted for publication in Int. J. Mod. Phys.
Identifying Agile Requirements Engineering Patterns in Industry
Agile Software Development (ASD) is gaining in popularity in today´s business world. Industry is adopting agile methodologies both to accelerate value delivery and to enhance the ability to deal with changing requirements. However, ASD has a great impact on how Requirements Engineering (RE) is carried out in agile environments. The integration of Human-Centered Design (HCD) plays an important role due to the focus on user and stakeholder involvement. To this end, we aim to introduce agile RE patterns as main objective of this paper. On the one hand, we will describe our pattern mining process based on empirical research in literature and industry. On the other hand, we will discuss our results and provide two examples of agile RE patterns. In sum, the pattern mining process identifies 41 agile RE patterns. The accumulated knowledge will be shared by means of a web application.Ministerio de Economía y Competitividad TIN2013-46928-C3-3-RMinisterio de Economía y Competitividad TIN2016-76956-C3-2-RMinisterio de Economía y Competitividad TIN2015-71938-RED
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