12,181 research outputs found
Breaking the core-envelope symmetry in p-mode pulsating stars
It has been shown that there is a potential ambiguity in the asteroseismic
determination of the location of internal structures in a pulsating star. We
show how, in the case of high-order non-radial acoustic modes, it is possible
to remove this ambiguity by considering modes of different degree. To support
our conclusions we have investigated the seismic signatures of sharp density
variations in the structure of quasi-homogeneous models.Comment: 3 pages, 3 figures, accepted for publication in Astronomy and
Astrophysic
Tuning the Mott transition in a Bose-Einstein condensate by multi-photon absorption
We study the time-dependent dynamics of a Bose-Einstein condensate trapped in
an optical lattice. Modeling the system as a Bose-Hubbard model, we show how
applying a periodic driving field can induce coherent destruction of tunneling.
In the low-frequency regime, we obtain the novel result that the destruction of
tunneling displays extremely sharp peaks when the driving frequency is resonant
with the depth of the trapping potential (``multi-photon resonances''), which
allows the quantum phase transition between the Mott insulator and the
superfluid state to be controlled with high precision. We further show how the
waveform of the field can be chosen to maximize this effect.Comment: Minor changes, this version to be published in Phys. Rev. Let
Taking individual heterogeneity in mortality risks into account in demographic studies of wild animal populations: development and use of statistical models.
The Cormarck-Jolly-Seber model incorporating frailty implemented in WinBUGS, using the 9000 kittiwake’s dataset monitorized during 22 years, showed that the convergence is very low over computational view. We developed different kind of multistate model, considering independence/dependence between random effect of breeding and survival probability. The last part of the work was dedicated to model selection with Bayesian framework
-Kicked Quantum Rotors: Localization and `Critical' Statistics
The quantum dynamics of atoms subjected to pairs of closely-spaced
-kicks from optical potentials are shown to be quite different from the
well-known paradigm of quantum chaos, the singly--kicked system. We
find the unitary matrix has a new oscillating band structure corresponding to a
cellular structure of phase-space and observe a spectral signature of a
localization-delocalization transition from one cell to several. We find that
the eigenstates have localization lengths which scale with a fractional power
and obtain a regime of near-linear spectral variances
which approximate the `critical statistics' relation , where is related to the fractal
classical phase-space structure. The origin of the exponent
is analyzed.Comment: 4 pages, 3 fig
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