528 research outputs found
Bernstein modes in a weakly relativistic electron-positron plasma
The kinetic theory of weakly relativistic electron-positron plasmas, producing dispersion relations for the electrostatic Bernstein modes was addressed. The treatment presented preserves the full momentum dependence of the cyclotron frequency, albeit with a relaxation on the true relativistic form of the distribution function. The implications of this new treatment were confined largely to astrophysical plasmas, where relativistic electronpositron plasmas occur naturally
Finite Temperature Wave-Function Renormalization, A Comparative Analysis
We compare two competing theories regarding finite temperature wave-function
corrections for the process and for and
related processes of interest for primordial nucleosynthesis. Although the two
methods are distinct (as shown in ) they yield the same finite
temperature correction for all and processes. Both methods
yield an increase in the He/H ratio of .01% due to finite temperature
renormalization rather than a decrease of .16% as previously predicted.Comment: 12 pages, 3 figures. LaTe
Topological and topological-electronic correlations in amorphous silicon
In this paper, we study several structural models of amorphous silicon, and
discuss structural and electronic features common to all. We note spatial
correlations between short bonds, and similar correlations between long bonds.
Such effects persist under a first principles relaxation of the system and at
finite temperature. Next we explore the nature of the band tail states and find
the states to possess a filamentary structure. We detail correlations between
local geometry and the band tails.Comment: 7 pages, 11 figures, submitted to Journal of Crystalline Solid
What fraction of stars formed in infrared galaxies at high redshift?
Star formation happens in two types of environment: ultraviolet-bright
starbursts (like 30 Doradus and HII galaxies at low redshift and Lyman-break
galaxies at high redshift) and infrared-bright dust-enshrouded regions (which
may be moderately star-forming like Orion in the Galaxy or extreme like the
core of Arp 220). In this work I will estimate how many of the stars in the
local Universe formed in each type of environment, using observations of
star-forming galaxies at all redshifts at different wavelengths and of the
evolution of the field galaxy population.Comment: 7 pages, 0 figs, to appear in proceedings of "Starbursts - From 30
Doradus to Lyman break galaxies", edited by Richard de Grijs and Rosa M.
Gonzalez Delgado, published by Kluwe
A BQP-complete problem related to the Ising model partition function via a new connection between quantum circuits and graphs
We present a simple construction that maps quantum circuits to graphs and
vice-versa. Inspired by the results of D.A. Lidar linking the Ising partition
function with quadratically signed weight enumerators (QWGTs), we also present
a BQP-complete problem for the additive approximation of a function over
hypergraphs related to the generating function of Eulerian subgraphs for
ordinary graphs. We discuss connections with the Ising partition function.Comment: 12 pages, 2 figure
Social Experimentation as Reflection-in-A ction
We present the results of our review of some forty community-level interventions undertaken in the developing world over the past twenty years m order to reduce malnourishment in children. We argue that such interventions, if they are considered as social experiments, cannot be assimilated to models of quasi-experimental method. We propose an alternative model of experimentation, which we call "reflection-in-action", which seems to us better suited to account for the kinds ofvahdity and rigor attainable in situations such as these.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68568/2/10.1177_107554708400600101.pd
Pragmatic Software Innovation
Part 2: Creating Value through Software DevelopmentInternational audienceWe understand software innovation as concerned with introducing innovation into the development of software intensive systems, i.e. systems in which software development and/or integration are dominant considerations. Innovation is key in almost any strategy for competitiveness in existing markets, for creating new markets, or for curbing rising public expenses, and software intensive systems are core elements in most such strategies. Software innovation therefore is vital for about every sector of the economy. Changes in software technologies over the last decades have opened up for experimentation, learning, and flexibility in ongoing software projects, but how can this change be used to facilitate software innovation? How can a team systematically identify and pursue opportunities to create added value in ongoing projects? In this paper, we describe Deweyan pragmatism as the philosophical foundation for Essence – a software innovation methodology – where unknown options and needs emerge as part of the development process itself. The foundation is illustrated via a simple example
Felix Alexandrovich Berezin and his work
This is a survey of Berezin's work focused on three topics: representation
theory, general concept of quantization, and supermathematics.Comment: LaTeX, 27 page
Transverse Wave Propagation in Relativistic Two-fluid Plasmas in de Sitter Space
We investigate transverse electromagnetic waves propagating in a plasma in
the de Sitter space. Using the 3+1 formalism we derive the relativistic
two-fluid equations to take account of the effects due to the horizon and
describe the set of simultaneous linear equations for the perturbations. We use
a local approximation to investigate the one-dimensional radial propagation of
Alfv\'en and high frequency electromagnetic waves and solve the dispersion
relation for these waves numerically.Comment: 19 pages, 12 figure
The Potential for Neutrino Physics at Muon Colliders and Dedicated High Current Muon Storage Rings
Conceptual design studies are underway for muon colliders and other
high-current muon storage rings that have the potential to become the first
true ``neutrino factories''. Muon decays in long straight sections of the
storage rings would produce precisely characterized beams of electron and muon
type neutrinos of unprecedented intensity. This article reviews the prospects
for these facilities to greatly extend our capabilities for neutrino
experiments, largely emphasizing the physics of neutrino interactions.Comment: 107 pages, 16 figures, to be published in Physics Report
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