2,349 research outputs found
A model of short-range correlations in the charge response
The validity of a model treating the short-range correlations up to the first
order is studied by calculating the charge response of an infinite system and
comparing the obtained results with those of a Fermi Hypernetted Chain
calculation.Comment: 6 pages, 3 Postscript figures, to be published on Phys. Rev.
Multipartite entanglement dynamics in a cavity
We study the dynamics of two kinds of entanglement, and there interplay. On
one hand, the intrinsic entanglement within a central system composed by three
two level atoms, and measured by multipartite concurrence, on the other, the
entanglement between the central system and a cavity, acting as an environment,
and measured with purity. Using dipole-dipole and Ising interactions between
atoms we propose two Hamiltonians, a homogeneous and a quasi-homogeneous one.
We find an upper bound for concurrence as a function of purity, associated to
the evolution of the state. A lower bound is also observed for the
homogeneous case. In both situations, we show the existence of critical values
of the interaction, for which the dynamics of entanglement seem complex.Comment: 10 pages, closest to journal versio
An all-densities pedestrian simulator based on a dynamic evaluation of the interpersonal distances
In this paper we deal with pedestrian modeling, aiming at simulating crowd
behavior in normal and emergency scenarios, including highly congested mass
events. We are specifically concerned with a new agent-based,
continuous-in-space, discrete-in-time, nondifferential model, where pedestrians
have finite size and are compressible to a certain extent. The model also takes
into account the pushing behavior appearing at extreme high densities. The main
novelty is that pedestrians are not assumed to generate any kind of "field" in
the space around which determines the behavior of the crowd. Instead, the
behavior of each pedestrian solely relies on its knowledge of the environment
and the evaluation of interpersonal distances between it and the others. The
model is able to reproduce the concave/concave fundamental diagram with a
"double hump" (i.e. with a second peak) which shows up when body forces come
into play. We present several numerical tests (some of them being inspired by
the recent ISO 20414 standard), which show how the model can reproduce
classical self-organizing patterns
Quantized form factor shift in the presence of free electron laser radiation
In electron scattering, the target form factors contribute significantly to
the diffraction pattern and carry information on the target electromagnetic
charge distribution. Here we show that the presence of electromagnetic
radiation, as intense as currently available in Free Electron Lasers, shifts
the dependence of the target form factors by a quantity that depends on the
number of photons absorbed or emitted by the electron as well as on the
parameters of the electromagnetic radiation. As example, we show the impact of
intense ultraviolet and soft X-ray radiation on elastic electron scattering by
Ne-like Argon ion and by Xenon atom. We find that the shift brought by the
radiation to the form factor is in the order of some percent. Our results may
open up a new avenue to explore matter with the assistance of laser
A study of the structure of jet turbulence producing jet noise
Characteristics of turbulent structure of mixing region near outlet of circular subsonic jet and production of jet nois
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