25,526 research outputs found
Anderson localization on the Falicov-Kimball model with Coulomb disorder
The role of Coulomb disorder is analysed in the Anderson-Falicov-Kimball
model. Phase diagrams of correlated and disordered electron systems are
calculated within dynamical mean-field theory applied to the Bethe lattice, in
which metal-insulator transitions led by structural and Coulomb disorders and
correlation can be identified. Metallic, Mott insulator, and Anderson insulator
phases, as well as the crossover between them are studied in this perspective.
We show that Coulomb disorder has a relevant role in the phase-transition
behavior as the system is led towards the insulator regime
A Fractional Calculus of Variations for Multiple Integrals with Application to Vibrating String
We introduce a fractional theory of the calculus of variations for multiple
integrals. Our approach uses the recent notions of Riemann-Liouville fractional
derivatives and integrals in the sense of Jumarie. Main results provide
fractional versions of the theorems of Green and Gauss, fractional
Euler-Lagrange equations, and fractional natural boundary conditions. As an
application we discuss the fractional equation of motion of a vibrating string.Comment: Accepted for publication in the Journal of Mathematical Physics
(14/January/2010
Temporal Analysis of Activity Patterns of Editors in Collaborative Mapping Project of OpenStreetMap
In the recent years Wikis have become an attractive platform for social
studies of the human behaviour. Containing millions records of edits across the
globe, collaborative systems such as Wikipedia have allowed researchers to gain
a better understanding of editors participation and their activity patterns.
However, contributions made to Geo-wikis_wiki-based collaborative mapping
projects_ differ from systems such as Wikipedia in a fundamental way due to
spatial dimension of the content that limits the contributors to a set of those
who posses local knowledge about a specific area and therefore cross-platform
studies and comparisons are required to build a comprehensive image of online
open collaboration phenomena. In this work, we study the temporal behavioural
pattern of OpenStreetMap editors, a successful example of geo-wiki, for two
European capital cities. We categorise different type of temporal patterns and
report on the historical trend within a period of 7 years of the project age.
We also draw a comparison with the previously observed editing activity
patterns of Wikipedia.Comment: Submitte
Neutral heavy lepton production at next high energy linear colliders
The discovery potential for detecting new heavy Majorana and Dirac neutrinos
at some recently proposed high energy colliders is discussed. These
new particles are suggested by grand unified theories and superstring-inspired
models. For these models the production of a single heavy neutrino is shown to
be more relevant than pair production when comparing cross sections and
neutrino mass ranges.
The process is calculated
including on-shell and off-shell heavy neutrino effects.
We present a detailed study of cross sections and distributions that shows a
clear separation between the signal and standard model contributions, even
after including hadronization effects.Comment: 4 pages including 15 figures, 1 table. RevTex. Accepted in Physical
Review
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