19,806 research outputs found
Synchronization in a ring of pulsating oscillators with bidirectional couplings
We study the dynamical behavior of an ensemble of oscillators interacting
through short range bidirectional pulses. The geometry is 1D with periodic
boundary conditions. Our interest is twofold. To explore the conditions
required to reach fully synchronization and to invewstigate the time needed to
get such state. We present both theoretical and numerical results.Comment: Revtex, 4 pages, 2 figures. To appear in Int. J. Bifurc. and Chao
Speeding up antidynamical Casimir effect with nonstationary qutrits
The antidynamical Casimir effect (ADCE) is a term coined to designate the
coherent annihilation of excitations due to resonant external perturbation of
system parameters, allowing for extraction of quantum work from nonvacuum
states of some field. Originally proposed for a two-level atom (qubit) coupled
to a single cavity mode in the context of nonstationary quantum Rabi model, it
suffered from very low transition rate and correspondingly narrow resonance
linewidth. In this paper we show analytically and numerically that the ADCE
rate can be increased by at least one order of magnitude by replacing the qubit
by an artificial three-level atom (qutrit) in a properly chosen configuration.
For the cavity thermal state we demonstrate that the dynamics of the average
photon number and atomic excitation is completely different from the qubit's
case, while the behavior of the total number of excitations is qualitatively
similar yet significantly faster.Comment: 9 pages, 4 figure
A search for hydrogenated fullerenes in fullerene-containing planetary nebulae
Detections of C60 and C70 fullerenes in planetary nebulae (PNe) of the
Magellanic Clouds and of our own Galaxy have raised the idea that other forms
of carbon such as hydrogenated fullerenes (fulleranes like C60H36 and C60H18),
buckyonions, and carbon nanotubes, may be widespread in the Universe. Here we
present VLT/ISAAC spectra (R ~600) in the 2.9-4.1 microns spectral region for
the Galactic PNe Tc 1 and M 1-20, which have been used to search for
fullerene-based molecules in their fullerene-rich circumstellar environments.
We report the non-detection of the most intense infrared bands of several
fulleranes around ~3.4-3.6 microns in both PNe. We conclude that if fulleranes
are present in the fullerene-containing circumstellar environments of these
PNe, then they seem to be by far less abundant than C60 and C70. Our
non-detections together with the (tentative) fulleranes detection in the
proto-PN IRAS 01005+7910 suggest that fulleranes may be formed in the short
transition phase between AGB stars and PNe but they are quickly destroyed by
the UV radiation field from the central star.Comment: Accepted for publication in Astronomy & Astrophysics (7 pages, 3
figures, and 3 Tables
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