13,005 research outputs found
Destination images of non-visitors
This article provides much needed understanding of destination images held by non-visitors. Recognizing the characteristics of non-visitor images and their formation is important in order to understand images more widely. This qualitative study assesses images of London. The views of three hundred people in the Czech Republic who have never visited London were obtained via an innovative open-ended research instrument. The study showed that non-visitors imagine destinations through comparisons with their own experiences of places. Findings indicate that images can be very persistent and that the first images formed of a destination endure over time. Although the research is based on people with no direct experience of London, the research highlights that a range of secondary ‘experiences’ influence image formation
Single photon production by rephased amplified spontaneous emission
The production of single photons using rephased amplified spontaneous
emission is examined. This process produces single photons on demand with high
efficiency by detecting the spontaneous emission from an atomic ensemble, then
applying a population-inverting pulse to rephase the ensemble and produce a
photon echo of the spontaneous emission events. The theoretical limits on the
efficiency of the production are determined for several variants of the scheme.
For an ensemble of uniform optical density, generating the initial spontaneous
emission and its echo using transitions of different strengths is shown to
produce single photons at 70% efficiency, limited by reabsorption. Tailoring
the spatial and spectral density of the atomic ensemble is then shown to
prevent reabsorption of the rephased photon, resulting in emission efficiency
near unity
A Mesolithic settlement site at Howick, Northumberland: a preliminary report
Excavations at a coastal site at Howick during 2000 and 2002 have revealed evidence for a substantial Mesolithic settlement and a Bronze Age cist cemetery. Twenty one radiocarbon determinations of the earlier eighth millennium BP (Cal.) indicate that the Mesolithic site is one of the earliest known in northern Britain. An 8m core of sediment was recovered from stream deposits adjacent to the archaeological site which provides information on local environmental conditions. Howick offers a unique opportunity to understand aspects of hunter-gatherer colonisation and settlement during a period of rapid palaeogeographical change around the margins of the North Sea basin, at a time when it was being progressively inundated by the final stages of the postglacial marine transgression. The cist cemetery will add to the picture of Bronze Age occupation of the coastal strip and again reveals a correlation between the location of Bronze Age and Mesolithic sites which has been observed elsewhere in the region
Analytic Approach to Perturbative QCD
The two-loop invariant (running) coupling of QCD is written in terms of the
Lambert W function. The analyticity structure of the coupling in the complex
Q^2-plane is established. The corresponding analytic coupling is reconstructed
via a dispersion relation. We also consider some other approximations to the
QCD beta-function, when the corresponding couplings are solved in terms of the
Lambert function. The Landau gauge gluon propagator has been considered in the
renormalization group invariant analytic approach (IAA). It is shown that there
is a nonperturbative ambiguity in determination of the anomalous dimension
function of the gluon field. Several analytic solutions for the propagator at
the one-loop order are constructed. Properties of the obtained analytical
solutions are discussed.Comment: Latex-file, 19 pages, 2 tables, 51 references, to be published in
Int. J. Mod. Phys.
The social psychology of citizenship: engagement with citizenship studies and future research
In this article we review the argument outlined in the opening article in this special thematic section: that the current social psychology of citizenship can be understood as the development of longstanding conceptualisations of the concept within the discipline. These conceptualisations have contributed to the current social psychological study of the constructive, active and collective (but often exclusive) understandings of citizenship in people’s everyday lives, as evidenced by contributions to this thematic section. We consider how this emerging body of work might fit with current citizenship studies and in particular how it may contribute to the current trend towards conceiving citizenship as an active practice embedded in everyday social life. Specifically, we highlight three areas of future research that we think are particularly promising: citizenship and recognition; displays and enactments of citizenship in public space; citizenship and lived coexistence. Although this is far from an exhaustive list of possibilities, we propose that research in these areas could enable the way for social psychology to articulate a distinct, recognisable and valuable contribution to citizenship studies
Engineering steady states using jump-based feedback for multipartite entanglement generation
We investigate the use of quantum-jump-based feedback to manipulate the
stability of multipartite entangled dark states in an open quantum system.
Using the model proposed in Phys. Rev. A 76, 010301(R) (2007) for a pair of
atoms, we show a general strategy to produce many-body singlet stationary
entangled states for larger number of atoms. In the case of four qubits, we
propose a simple local feedback control that, although not optimal, is
realistic and stabilises a highly entangled state. We discuss the limitations
and analyse alternative strategies within the framework of direct jump feedback
schemes.Comment: 9 pages, 8 figure
Effect of weak magnetic field on polariton-electron scattering in semiconductor microcavities
We theoretically calculate the polariton linewidth associated with the
polariton-electron scattering in a microcavity in presence of a magnetic field
perpendicular to the microcavity plane. It is shown that the polariton
linewidth oscillates as a function of the magnetic field magnitude and the
polariton-electron scattering rate can be not only decreased but also increased
by the magnetic field. The possible applications of such an effect are
discussed.Comment: LaTex, 6 pages, 3 figure
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