13,576 research outputs found
Linear and nonlinear coupling of quantum dots in microcavities
We discuss the topical and fundamental problem of strong-coupling between a
quantum dot an the single mode of a microcavity. We report seminal quantitative
descriptions of experimental data, both in the linear and in the nonlinear
regimes, based on a theoretical model that includes pumping and quantum
statistics.Comment: Proceedings of the symposium Nanostructures: Physics and Technology
2010 (http://www.ioffe.ru/NANO2010), 2 pages in proceedings styl
Dynamics of formation and decay of coherence in a polariton condensate
We study the dynamics of formation and decay of a condensate of microcavity
polaritons. We investigate the relationship between the number of particles,
the emission's linewidth and its degree of linear polarization which serves as
the order parameter. Tracking the condensate's formation, we show that, even
when interactions are negligible, coherence is not determined only by
occupation of the ground state. As a result of the competition between the
coherent and thermal fractions of the condensate, the highest coherence is
obtained some time after the particle number has reached its maximum
Superconducting/magnetic three state nanodevice for memory and reading applications
We present a simple nanodevice that can operate in two modes: i) three-state
memory and ii) reading device. The nanodevice is fabricated with an array of
ordered triangular-shaped nanomagnets embedded in a superconducting thin film.
The input signal is ac current and the output signal is dc voltage. Vortex
ratchet effect in combination with out of plane magnetic anisotropy of the
nanomagnets is the background physics which governs the nanodevice performance.Comment: 10 pages, 4 figure
Scaling of the conductance in gold nanotubes
A new form of gold nanobridges has been recently observed in ultrahigh-vacuum
experiments, where the gold atoms rearrange to build helical nanotubes, akin in
some respects to carbon nanotubes. The good reproducibility of these wires and
their unexpected stability will allow for conductance measurements and make
them promising candidates for future applications . We present here a study of
the transport properties of these nanotubes in order to understand the role of
chirality and of the different orbitals in quantum transport observables. The
conductance per atomic row shows a light decreasing trend as the diameter
grows, which is also shown through an analytical formula based on a one-orbital
model.Comment: 5 pages, 6 figure
Density operator of a system pumped with polaritons: A Jaynes-Cummings like approach
We investigate the effects of considering two different incoherent pumpings
over a microcavity-quantum dot system modelled using the Jaynes-Cummings
Hamiltonian. When the system is incoherently pumped with polaritons it is able
to sustain a large number of photons inside the cavity with Poisson-like
statistics in the stationary limit, and also leads to a separable
exciton-photon state. We also investigate the effects of both types of pumpings
(Excitonic and Polaritonic) in the emission spectrum of the cavity. We show
that the polaritonic pumping as considered here is unable to modify the
dynamical regimes of the system as the excitonics pumping does. Finally, we
obtain a closed form expression for the negativity of the density matrices that
the quantum master equation considered here generates.Comment: 16 pages, 4 figure
Five supernova survey galaxies in the southern hemisphere. II. The supernova rates
Based on the database compiled in the first article of this series, with 56
SN events discovered in 3838 galaxies of the southern hemisphere, we compute
the rate of supernovae (SNe) of different types along the Hubble sequence
normalized to the optical and near-infrared luminosities as well as to the
stellar mass of the galaxies. We find that the rates of all SN types show a
dependence on both morphology and colors of the galaxies, and therefore, on the
star-formation activity. The rate of core-collapse (CC) SNe is confirmed to be
closely related to the Star Formation Rate (SFR) and only indirectly to the
total mass of the galaxies. The rate of SNe Ia can be explained by assuming
that at least 15% of Ia events in spiral galaxies originates in relatively
young stellar populations. We find that the rates show no modulation with
nuclear activity or environment. The ratio of SN rates between types Ib/c and
II shows no trend with spiral type.Comment: 13 pages, 2 figures, 5 tables, published in Astrophysics (English
translation of Astrofizika
GW170817: implications for the local kilonova rate and for surveys from ground-based facilities
We compute the local rate of events similar to GRB 170817A, which has been
recently found to be associated with a kilonova (KN) outburst. Our analysis
finds an observed rate of such events of R
Gpcyr. After comparing at their face values this density of sGRB
outbursts with the much higher density of Binary Neutron Star (BNS) mergers of
1540 Gpcyr, estimated by LIGO-Virgo
collaboration, one can conclude, admittedly with large uncertainty that either
only a minor fraction of BNS mergers produces sGRB/KN events or the sGRBs
associated with BNS mergers are beamed and observable under viewing angles as
large as . Finally we provide preliminary estimates
of the number of sGRB/KN events detected by future surveys carried out with
present/future ground-based/space facilities, such as LSST, VST, ZTF, SKA and
THESEUS.Comment: MNRAS accepted, 6 pages, 1 figur
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