9,606 research outputs found
Dynamical aspects of Kinouchi-Copelli model: emergence of avalanches at criticality
We analyze the behavior of bursts of neural activity in the Kinouchi-Copelli
model, originally conceived to explain information processing issues in sensory
systems. We show that, at a critical condition, power-law behavior emerges for
the size and duration of the bursts (avalanches), with exponents experimentally
observed in real biological systems.Comment: Paper accepted for Brazilian Conference on Dynamics, Control and
Applications (oral presentation and poster). 4 pages, 5 figure
Young and embedded clusters in Cygnus-X: evidence for building up the IMF?
We provide a new view on the Cygnus-X north complex by accessing for the
first time the low mass content of young stellar populations in the region.
CFHT/WIRCam camera was used to perform a deep near-IR survey of this complex,
sampling stellar masses down to ~0.1 M. Several analysis tools,
including a extinction treatment developed in this work, were employed to
identify and uniformly characterise a dozen unstudied young star clusters in
the area. Investigation of their mass distributions in low-mass domain revealed
a relatively uniform log-normal IMF with a characteristic mass of 0.320.08
M and mass dispersion of 0.400.06. In the high mass regime, their
derived slopes showed that while the youngest clusters (age < 4 Myr) presented
slightly shallower values with respect to the Salpeter's, our older clusters (4
Myr < age < 18 Myr) showed IMF compliant values and a slightly denser stellar
population. Although possibly evidencing a deviation from an 'universal' IMF,
these results also supports a scenario where these gas dominated young clusters
gradually 'build up' their IMF by accreting low-mass stars formed in their
vicinity during their first ~3 Myr, before the gas expulsion phase, emerging at
the age of ~4 Myr with a fully fledged IMF. Finally, the derived distances to
these clusters confirmed the existence of at least 3 different star forming
regions throughout Cygnus-X north complex, at distances of 500-900 pc, 1.4-1.7
kpc and 3.0 kpc, and revealed evidence of a possible interaction between some
of these stellar populations and the Cygnus-OB2 association.Comment: 20 pages, 19 figures. Contains an appendix with 10 extra figure
Roughness correction to the Casimir force : Beyond the Proximity Force Approximation
We calculate the roughness correction to the Casimir effect in the parallel
plates geometry for metallic plates described by the plasma model. The
calculation is perturbative in the roughness amplitude with arbitrary values
for the plasma wavelength, the plate separation and the roughness correlation
length. The correction is found to be always larger than the result obtained in
the Proximity Force Approximation.Comment: 7 pages, 3 figures, v2 with minor change
An alternative theoretical approach to describe planetary systems through a Schrodinger-type diffusion equation
In the present work we show that planetary mean distances can be calculated
with the help of a Schrodinger-type diffusion equation. The obtained results
are shown to agree with the observed orbits of all the planets and of the
asteroid belt in the solar system, with only three empty states. Furthermore,
the equation solutions predict a fundamental orbit at 0.05 AU from solar-type
stars, a result confirmed by recent discoveries. In contrast to other similar
approaches previously presented in the literature, we take into account the
flatness of the solar system, by considering the flat solutions of the
Schrodinger-type equation. The model has just one input parameter, given by the
mean distance of Mercury.Comment: 6 pages. Version accepted for publication in Chaos, Solitons &
Fractal
Particle Creation by a Moving Boundary with Robin Boundary Condition
We consider a massless scalar field in 1+1 dimensions satisfying a Robin
boundary condition (BC) at a non-relativistic moving boundary. We derive a
Bogoliubov transformation between input and output bosonic field operators,
which allows us to calculate the spectral distribution of created particles.
The cases of Dirichlet and Neumann BC may be obtained from our result as
limiting cases. These two limits yield the same spectrum, which turns out to be
an upper bound for the spectra derived for Robin BC. We show that the particle
emission effect can be considerably reduced (with respect to the
Dirichlet/Neumann case) by selecting a particular value for the oscillation
frequency of the boundary position
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