13,864 research outputs found
Recurrence and transience for long-range reversible random walks on a random point process
We consider reversible random walks in random environment obtained from
symmetric long--range jump rates on a random point process. We prove almost
sure transience and recurrence results under suitable assumptions on the point
process and the jump rate function. For recurrent models we obtain almost sure
estimates on effective resistances in finite boxes. For transient models we
construct explicit fluxes with finite energy on the associated electrical
network.Comment: 34 page
Diffusivity in one-dimensional generalized Mott variable-range hopping models
We consider random walks in a random environment which are generalized
versions of well-known effective models for Mott variable-range hopping. We
study the homogenized diffusion constant of the random walk in the
one-dimensional case. We prove various estimates on the low-temperature
behavior which confirm and extend previous work by physicists.Comment: Published in at http://dx.doi.org/10.1214/08-AAP583 the Annals of
Applied Probability (http://www.imstat.org/aap/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Synchronization in fiber lasers arrays
We consider an array of fiber lasers coupled through the nearest neighbors.
The model is a generalized nonlinear Schroedinger equation where the usual
Laplacian is replaced by the graph Laplacian. For a graph with no symmetries,
we show that there is no resonant transfer of energy between the different
eigenmodes. We illustrate this and confirm our result on a simple graph. This
shows that arrays of fiber ring lasers can be made temporally coherent
Invariance principle for Mott variable range hopping and other walks on point processes
We consider a random walk on a homogeneous Poisson point process with energy
marks. The jump rates decay exponentially in the A-power of the jump length and
depend on the energy marks via a Boltzmann--like factor. The case A=1
corresponds to the phonon-induced Mott variable range hopping in disordered
solids in the regime of strong Anderson localization. We prove that for almost
every realization of the marked process, the diffusively rescaled random walk,
with arbitrary start point, converges to a Brownian motion whose diffusion
matrix is positive definite, and independent of the environment. Finally, we
extend the above result to other point processes including diluted lattices.Comment: 47 pages, minor corrections, submitte
Awareness towards Chikungunya virus infection risk by general practitioners in Rome: a questionnaire based survey before the 2017 outbreak
Autochthonous cases of Chikungunya (CHIKV) have been recently detected in Rome. A survey was conduct- ed prior to the 2017 outbreak to assess knowledge, attitude, and practices towards CHIKV infections on 103 randomly selected general practitioners (GPs), practicing in the centre of Rome. Only 24.3% were aware of CHIKV and completed the interview. Among completers, the knowledge of basic elements of CHIKV in- fection was insufficient. Only two thirds of them were able to identify possible CHIKV cases in hypothetical clinical scenarios presented by the interviewer. Our study highlights the need to improve GP knowledge to- wards CHIKV, as a necessary step to establish an efficacious epidemic surveillance
Detecting the Stimulated Decay of Axions at Radio Frequencies
Assuming axion-like particles account for the entirety of the dark matter in
the Universe, we study the possibility of detecting their decay into photons at
radio frequencies. We discuss different astrophysical targets, such as dwarf
spheroidal galaxies, the Galactic Center and halo, and galaxy clusters. The
presence of an ambient radiation field leads to a stimulated enhancement of the
decay rate; depending on the environment and the mass of the axion, the effect
of stimulated emission may amplify the photon flux by serval orders of
magnitude. For axion-photon couplings allowed by astrophysical and laboratory
constraints(and possibly favored by stellar cooling), we find the signal to be
within the reach of next-generation radio telescopes such as the Square
Kilometer Array.Comment: Minor changes, references added, matches published versio
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