3,760 research outputs found
Reversibility and Non-reversibility in Stochastic Chemical Kinetics
Mathematical problems with mean field and local type interaction related to
stochastic chemical kinetics,are considered. Our main concern various
definitions of reversibility, their corollaries (Boltzmann type equations,
fluctuations, Onsager relations, etc.) and emergence of irreversibility
Localization properties of one-dimensional Frenkel excitons: Gaussian versus Lorentzian diagonal disorder
We compare localization properties of one-dimensional Frenkel excitons with
Gaussian and Lorentzian uncorrelated diagonal disorder. We focus on the states
of the Lifshits tail, which dominate the optical response and low-temperature
energy transport in molecular J-aggregates. The absence of exchange narrowing
in chains with Lorentzian disorder is shown to manifest itself in the disorder
scaling of the localization length distribution. Also, we show that the local
exciton level structure of the Lifshits tail differs substantially for these
two types of disorder: In addition to the singlets and doublets of localized
states near the bare band edge, strongly resembling those found for Gaussian
disorder, for Lorentzian disorder two other types of states are found in this
energy region as well, namely multiplets of three or four states localized on
the same chain segment and isolated states localized on short segments.
Finally, below the Lifshits tail, Lorentzian disorder induces strongly
localized exciton states, centered around low energy sites, with localization
properties that strongly depend on energy. For Gaussian disorder with a
magnitude that does not exceed the exciton bandwidth, the likelihood to find
such very deep states is exponentially small.Comment: 9 two-column pages, 4 figures, to appear in Phys. Rev.
Tailoring optical response of a hybrid comprising a quantum dimer emitter strongly coupled to a metal nanoparticle
We study theoretically the optical response of a nanohybrid comprising a
symmetric quantum dimer emitter coupled to a metal nanoparticle (MNP). The
interactions between the exitonic transitions in the dimer and the plasmons in
the MNP lead to novel effects in the composite's input-output characteristics
for the light intensity and the absorption spectrum, which we study in the
linear and nonlinear regimes. We fnd that the exciton-plasmon hybridization
leads to optical bistability and hysteresis for the one-exciton transition and
enhancement of excitation for the two-exciton transition. The latter leads to a
signifcant decrease of the field strength needed to saturate the system. In the
linear regime, the absortion spectrum has a dispersive (Fano-like) line shape.
The spectral position and shape of this spectrum depend on the detuning of the
dimer's one-exciton resonance relative to the plasmon resonance. Upon
increasing the applied field intensity to the nonlinear regime, the Fano-like
singularities in the absorption spectra are smeared and they disappear due to
the saturation of the dimer, which leads to the MNP dominating the spectrum.
The above effects, for which we provide physical explanations, allow one to
tailor the Fano-like shape of the absorption spectrum, by changing either the
detuning or the input power
Particle Event Generator: A Simple-in-Use System PEGASUS version 1.0
PEGASUS is a parton-level Monte-Carlo event generator designed to calculate
cross sections for a wide range of hard QCD processes at high energy and
collisions, which incorporates the dynamics of transverse momentum
dependent (TMD) parton distributions in a proton. Being supplemented with
off-shell production amplitudes for a number of partonic subprocesses and
provided with necessary TMD gluon density functions, it produces weighted or
unweighted event records which can be saved as a plain data file or a file in a
commonly used Les Houches Event format. A distinctive feature of PEGASUS is an
intuitive and extremely user friendly interface, allowing one to easily
implement various kinematical cuts into the calculations. Results can be also
presented "on the fly" with built-in tool \textsc{pegasus plotter}. A short
theoretical basis is presented and detailed program description is given.Comment: 24 pages, 8 figure
Response to the Comment on "Excitons in Molecular Aggregates with L\'evy Disorder: Anomalous Localization and Exchange Broadening of Optical Spectra"
In previous work, we have predicted novel effects, such as exchange
broadening, anomalous scaling of the localization length and a blue shift of
the absorption spectrum with increasing disorder strength, for static disorder
models described by stable distributions with stability index {\alpha}<1. The
main points of the Comment are that the outliers introduced by heavy tails in
the disorder distribution (i) do not lead to deviations from the conventional
scaling law for the half width at half maximum (HWHM) of the absorption
spectrum and (ii) do not lead to non-universality of the distribution of
localization lengths. We show below that the findings reported by us in the
Letter are correct and that the wrong conclusions of the Comment arise from
focusing on small {\sigma} values.Comment: Based on our response submitted to Physical Review Letters on January
20, 2012. We now also take into account the modifications made to the Comment
upon resubmission of the Comment. The Reply has been accepted in Physical
Review Letter
FPT-algorithms for some problems related to integer programming
In this paper, we present FPT-algorithms for special cases of the shortest
lattice vector, integer linear programming, and simplex width computation
problems, when matrices included in the problems' formulations are near square.
The parameter is the maximum absolute value of rank minors of the corresponding
matrices. Additionally, we present FPT-algorithms with respect to the same
parameter for the problems, when the matrices have no singular rank
sub-matrices.Comment: arXiv admin note: text overlap with arXiv:1710.00321 From author:
some minor corrections has been don
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