812 research outputs found
Neutron Star Vortex Dynamics and Magnetic Field Decay: Implications for High Density Nuclear Matter
We investigate the effect of the density-dependent proton and neutron gaps on
vortex dynamics in neutron stars. We argue that the persistence of neutron star
magnetic fields on timescales of y suggests a superconducting gap curve
with local maximum at intermediate density. We discuss the implications for
exotic core phenomena such as pion/kaon condensation or a transition to quark
matter.Comment: 7 pages, 2 figures, uses LaTe
Multicultural Engagements in Lived Spaces: How Cultural Communities Intersect in Belleville, Paris
The need to contend with greater diversity in cities raises the question of the level and timbre of group interactions. This study examines how diversity at a small scale operates and the conditions under which it may lead to true engagement, parallel lives, detachment, or hostility. The site is the multicultural Parisian neighborhood of Belleville, with a focus on the behaviors and attitudes of merchants who work there. Data gathering comprised observation and examination of neighborhood dynamics, the distribution of various businesses, and the nature of customer and everyday traffic as well as 34 structured interviews. Our findings show the significant Chinese population and businesses separated from the rest of the district and the other businesses. This separation is reinforced with a large degree of mutual distrust. However, relations between Arabs and Jews, tense at larger scales, are harmonious though increasingly tinged by outside worries. Multicultural relations observed on the ground differ from those apparent at larger scales, reaffirming the importance of place and local circumstances
Vibrational properties of phonons in random binary alloys: An augmented space recursive technique in the k-representation
We present here an augmented space recursive technique in the
k-representation which include diagonal, off-diagonal and the environmental
disorder explicitly : an analytic, translationally invariant, multiple
scattering theory for phonons in random binary alloys.We propose the augmented
space recursion (ASR) as a computationally fast and accurate technique which
will incorporate configuration fluctuations over a large local environment. We
apply the formalism to , Ni_{88}Cr_12} and
alloys which is not a random choice. Numerical results on spectral functions,
coherent structure factors, dispersion curves and disordered induced FWHM's are
presented. Finally the results are compared with the recent itinerant coherent
potential approximation (ICPA) and also with experiments.Comment: 20 pages, LaTeX, 23 figure
A High Power Hydrogen Target for Parity Violation Experiments
Parity-violating electron scattering measurements on hydrogen and deuterium,
such as those underway at the Bates and CEBAF laboratories, require
luminosities exceeding cms, resulting in large beam
power deposition into cryogenic liquid. Such targets must be able to absorb 500
watts or more with minimal change in target density. A 40~cm long liquid
hydrogen target, designed to absorb 500~watts of beam power without boiling,
has been developed for the SAMPLE experiment at Bates. In recent tests with
40~A of incident beam, no evidence was seen for density fluctuations in
the target, at a sensitivity level of better than 1\%. A summary of the target
design and operational experience will be presented.Comment: 13 pages, 9 postscript figure
Particle physics models of inflation
Inflation models are compared with observation on the assumption that the
curvature perturbation is generated from the vacuum fluctuation of the inflaton
field. The focus is on single-field models with canonical kinetic terms,
classified as small- medium- and large-field according to the variation of the
inflaton field while cosmological scales leave the horizon. Small-field models
are constructed according to the usual paradigm for beyond Standard Model
physicsComment: Based on a talk given at the 22nd IAP Colloquium, ``Inflation +25'',
Paris, June 2006 Curve omitted from final Figur
Challenges of open innovation: the paradox of firm investment in open-source software
Open innovation is a powerful framework encompassing the generation, capture, and employment of intellectual property at the firm level. We identify three fundamental challenges for firms in applying the concept of open innovation: finding creative ways to exploit internal innovation, incorporating external innovation into internal development, and motivating outsiders to supply an ongoing stream of external innovations. This latter challenge involves a paradox, why would firms spend money on R&D efforts if the results of these efforts are available to rival firms? To explore these challenges, we examine the activity of firms in opensource software to support their innovation strategies. Firms involved in open-source software often make investments that will be shared with real and potential rivals. We identify four strategies firms employ – pooled R&D/product development, spinouts, selling complements and attracting donated complements – and discuss how they address the three key challenges of open innovation. We conclude with suggestions for how similar strategies may apply in other industries and offer some possible avenues for future research on open innovation
Managing the trade-off implications of global supply
The cost versus response trade-off is a growing logistics issue due to many markets being increasingly characterized by demand uncertainty and shorter product life cycles. This is exacerbated further with supply increasingly moving to low cost global sources. However, the poor response implications of global supply are often not addressed or even acknowledged when undertaking such decisions. Consequently, various practical approaches to minimising, postponing or otherwise managing the impact of the demand uncertainty are often only adopted retrospectively. Even though such generic solutions are documented through case examples we lack effective tools and concepts to support the proactive identification and resolution of such trade-offs. This paper reports on case-based theory building research, involving three cases from the UK and USA used in developing a conceptual model with associated tools, in support of such a process
The Effective Field Theory of Inflation
We study the effective field theory of inflation, i.e. the most general
theory describing the fluctuations around a quasi de Sitter background, in the
case of single field models. The scalar mode can be eaten by the metric by
going to unitary gauge. In this gauge, the most general theory is built with
the lowest dimension operators invariant under spatial diffeomorphisms, like
g^{00} and K_{mu nu}, the extrinsic curvature of constant time surfaces. This
approach allows us to characterize all the possible high energy corrections to
simple slow-roll inflation, whose sizes are constrained by experiments. Also,
it describes in a common language all single field models, including those with
a small speed of sound and Ghost Inflation, and it makes explicit the
implications of having a quasi de Sitter background. The non-linear realization
of time diffeomorphisms forces correlation among different observables, like a
reduced speed of sound and an enhanced level of non-Gaussianity.Comment: 26 pages. v2: minor corrections, JHEP published versio
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