12,146 research outputs found
Spectral Characters of Finite-Dimensional Representations of Affine Algebras
We introduce the notion of a spectral character for finite-dimensional
representations of affine algebras. These can be viewed as a suitable q=1 limit
of the elliptic characters defined by Etingof and Moura for quantum affine
algebras. We show that these characters determine blocks of the category of
finite-dimensional modules for affine algebras. To do this we use the Weyl
modules defined by Chari and Pressley and some indecomposable reducible
quotient of the Weyl modules.Comment: More concise proofs for Propositions 1.2 and 2.4 added. To appear in
Journal of Algebr
Scalable Detection and Isolation of Phishing
This paper presents a proposal for scalable detection and isolation of phishing. The main ideas are to move the protection from end users towards the network provider and to employ the novel bad neighborhood concept, in order to detect and isolate both phishing e-mail senders and phishing web servers. In addition, we propose to develop a self-management architecture that enables ISPs to protect their users against phishing attacks, and explain how this architecture could be evaluated. This proposal is the result of half a year of research work at the University of Twente (UT), and it is aimed at a Ph.D. thesis in 2012
New Analyses of Double-Bang Events in the Atmosphere
We use CORSIKA+Herwig simulation code to produce ultra-high energy neutrino
interactions in the atmosphere. Our aim is to reproduce extensive air showers
originated by extragalactic tau-neutrinos. For charged current tau-neutrino
interactions in the atmosphere, beside the air shower originated from the
neutrino interaction, it is expected that a tau is created and may decay before
reaching the ground. That phenomenon makes possible the generation of two
related extensive air showers, the so called Double-Bang event. We make an
analysis of the main characteristics of Double-Bang events in the atmosphere
for mean values of the parameters involved in such phenomenon, like the
inelasticity and tau decay length. We discuss what may happen for the ``out of
the average'' cases and conclude that it may be possible to observe this kind
of event in ultra-high energy cosmic ray observatories such as Pierre Auger or
Telescope Array.Comment: 17 pages, 5 figures, final version to appear in BJ
Scalar Dark Matter in light of LEP and ILC Experiments
In this work we study a scalar field dark matter model with mass of the order
of 100 MeV. We assume dark matter is produced in the process , that, in fact, could be a background for the standard process
extensively studied at LEP. We constrain the
chiral couplings, and , of the dark matter with electrons through an
intermediate fermion of mass GeV and obtain and
for the best fit point of our analysis. We also
analyze the potential of ILC to detect this scalar dark matter for two
configurations: (i) center of mass energy GeV and luminosity
fb, and (ii) center of mass energy TeV
and luminosity fb. The differences of polarized beams
are also explored to better study the chiral couplings.Comment: 15 pages, 6 figures and 1 table. New references added and
improvements in the text. Conclusions unchange
Spatio-temporal conjecture for diffusion
We present here a conjecture about the equivalence between the noise density
of states of a system governed by a generalized Langevin equation and the
fluctuation in the energy density of states in a Hamiltonian system. We present
evidence of this for a disordered Heisenberg system.Comment: 6 pages, 1 figure. Submitted to Physica
Distributing the Kalman Filter for Large-Scale Systems
This paper derives a \emph{distributed} Kalman filter to estimate a sparsely
connected, large-scale, dimensional, dynamical system monitored by a
network of sensors. Local Kalman filters are implemented on the
(dimensional, where ) sub-systems that are obtained after
spatially decomposing the large-scale system. The resulting sub-systems
overlap, which along with an assimilation procedure on the local Kalman
filters, preserve an th order Gauss-Markovian structure of the centralized
error processes. The information loss due to the th order Gauss-Markovian
approximation is controllable as it can be characterized by a divergence that
decreases as . The order of the approximation, , leads to a lower
bound on the dimension of the sub-systems, hence, providing a criterion for
sub-system selection. The assimilation procedure is carried out on the local
error covariances with a distributed iterate collapse inversion (DICI)
algorithm that we introduce. The DICI algorithm computes the (approximated)
centralized Riccati and Lyapunov equations iteratively with only local
communication and low-order computation. We fuse the observations that are
common among the local Kalman filters using bipartite fusion graphs and
consensus averaging algorithms. The proposed algorithm achieves full
distribution of the Kalman filter that is coherent with the centralized Kalman
filter with an th order Gaussian-Markovian structure on the centralized
error processes. Nowhere storage, communication, or computation of
dimensional vectors and matrices is needed; only dimensional
vectors and matrices are communicated or used in the computation at the
sensors
Service scheduling in garden maintenance
Neoturf is a Portuguese company working in the area of project, building and garden’s maintenance. Neoturf would like to have a procedure for scheduling and routing efficiently the clients from garden maintenance services. The company has two teams available during the whole year and an additional team during summer to handle all the maintenance jobs. Each team consists of two or three employees with a vehicle fully equipped with the tools that allow to carry out every kind of maintenance service. In the beginning of each year, the number and frequency of maintenance interventions to conduct during the year, on each client, are accorded. Each client is assigned to the same team and, usually, time windows are established so that visits to the client should occur only within these periods. As the Neoturf costumers’ are geographically spread over a wide region, the total distance on visiting clients is a factor that has a heavy weight on the costs of the company. Neoturf is concerned with reducing these costs, while satisfying the agreements with the clients
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