4,730 research outputs found
Polariton condensation in photonic crystals with high molecular orientation
We study Frenkel exciton-polariton Bose-Einstein condensation in a
two-dimensional defect-free triangular photonic crystal with an organic
semiconductor active medium containing bound excitons with dipole moments
oriented perpendicular to the layers. We find photonic Bloch modes of the
structure and consider their strong coupling regime with the excitonic
component. Using the Gross- Pitaevskii equation for exciton polaritons and the
Boltzmann equation for the external exciton reservoir, we demonstrate the
formation of condensate at the points in reciprocal space where photon group
velocity equals zero. Further, we demonstrate condensation at non-zero momentum
states for TM-polarized photons in the case of a system with incoherent
pumping, and show that the condensation threshold varies for different points
in the reciprocal space, controlled by detuning.Comment: 6 pages, 4 figure
Quantum Zeno and anti-Zeno effects in the Friedrichs model
We analyze the short-time behavior of the survival probability in the frame
of the Friedrichs model for different formfactors. We have shown that this
probability is not necessary analytic at the time origin. The time when the
quantum Zeno effect could be observed is found to be much smaller than usually
estimated. We have also studied the anti-Zeno era and have estimated its
duration.Comment: References added. Appendix B shortened. Discussions extende
Superheavies: Theoretical incitements and predictions
It is well known that in fusion reactions one may get only neutron deficient
superheavy nuclei located far from the island of stability. The multi-nucleon
transfer reactions allow one to produce more neutron enriched new heavy nuclei
but the corresponding cross sections are rather low. Neutron capture process is
considered here as alternative method for production of long-lived neutron rich
superheavy nuclei. Strong neutron fluxes might be provided by nuclear reactors
and nuclear explosions in laboratory frame and by supernova explosions in
nature. All these cases are discussed in the paper.Comment: 7 FIGURE
Spectroscopic studies of fractal aggregates of silver nanospheres undergoing local restructuring
We present an experimental spectroscopic study of large random colloidal
aggregates of silver nanoparticles undergoing local restructuring. We argue
that such well-known phenomena as strong fluctuation of local electromagnetic
fields, appearance of "hot spots" and enhancement of nonlinear optical
responses depend on the local structure on the scales of several nanosphere
diameters, rather that the large-scale fractal geometry of the sample.Comment: 3.5 pages, submitted to J. Chem. Phy
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