46,155 research outputs found
Oscillatory convection in binary mixtures: thermodiffusion, solutal buoyancy, and advection
The role of thermodiffusive generation of concentration fluctuations via the
Soret effect, their contribution to the buoyancy forces that drive convection,
the advective mixing effect of the latter, and the diffusive homogenisation are
compared and elucidated for oscillatory convection. Numerically obtained
solutions of the field equations in the form of spatially extended relaxed
traveling waves, of standing waves, and of the transient growth of standing
waves and their transition to traveling waves are discussed as well as
spatially localized convective states of traveling waves that are surrounded by
the quiescent fluid.Comment: 30 pages, 10 figure
Stability boundaries of roll and square convection in binary fluid mixtures with positive separation ratio
Rayleigh-B\'{e}nard convection in horizontal layers of binary fluid mixtures
heated from below with realistic horizontal boundary conditions is studied
theoretically using multi-mode Galerkin expansions. For positive separation
ratios the main difference between the mixtures and pure fluids lies in the
existence of stable three dimensional patterns near onset in a wide range of
the parameter space. We evaluated the stationary solutions of roll, crossroll,
and square convection and we determined the location of the stability
boundaries for many parameter combinations thereby obtaining the Busse balloon
for roll and square patterns.Comment: 19 pages + 15 figures, accepted by Journal of Fluid Mechanic
Charmonia production from -hadron decays at LHC with -factorization: , and
We consider the production of and mesons originating from
the decays of -flavored hadrons at the LHC using the -factorization
approach. Our analysis covers both inclusive charmonia production and
production of mesons in association with bosons. We apply the
transverse momentum dependent (or unintegrated) gluon density in a proton
derived from Catani-Ciafaloni-Fiorani-Marchesini (CCFM) evolution equation and
adopt fragmentation functions based on the non-relativistic QCD factorization
to describe the inclusive -hadron decays into the different charmonium
states. Our predictions agree well with latest experimental data taken by the
CMS, ATLAS and LHCb Collaborations at , and ~TeV. The
contributions from double parton scattering to the associated non-prompt
production are estimated and found to be small.Comment: 12 pages, 5 figure
Transport in Almost Integrable Models: Perturbed Heisenberg Chains
The heat conductivity kappa(T) of integrable models, like the one-dimensional
spin-1/2 nearest-neighbor Heisenberg model, is infinite even at finite
temperatures as a consequence of the conservation laws associated with
integrability. Small perturbations lead to finite but large transport
coefficients which we calculate perturbatively using exact diagonalization and
moment expansions. We show that there are two different classes of
perturbations. While an interchain coupling of strength J_perp leads to
kappa(T) propto 1/J_perp^2 as expected from simple golden-rule arguments, we
obtain a much larger kappa(T) propto 1/J'^4 for a weak next-nearest neighbor
interaction J'. This can be explained by a new approximate conservation law of
the J-J' Heisenberg chain.Comment: 4 pages, several minor modifications, title change
Testing the parton evolution with the use of two-body final states
We consider the production of quarks and Drell-Yan lepton pairs at
LHC conditions focusing attention on the total transverse momentum of the
produced pair and on the azimuthal angle between the momenta of the outgoing
particles. Plotting the corresponding distributions in bins of the final state
invariant mass, one can reconstruct the full map of the transverse momentum
dependent parton densities in a proton. We give examples of how can these
distributions can look like at the LHC energies.Comment: 8 pages, 7 figure
Nonlinear Stochastic Resonance with subthreshold rectangular pulses
We analyze the phenomenon of nonlinear stochastic resonance (SR) in noisy
bistable systems driven by pulsed time periodic forces. The driving force
contains, within each period, two pulses of equal constant amplitude and
duration but opposite signs. Each pulse starts every half-period and its
duration is varied. For subthreshold amplitudes, we study the dependence of the
output signal-to-noise ratio (SNR) and the SR gain on the noise strength and
the relative duration of the pulses. We find that the SR gains can reach values
larger than unity, with maximum values showing a nonmonotonic dependence on the
duration of the pulses.Comment: 7 pages, 2 figure
Tripartite Entanglement in Noninertial Frame
The tripartite entanglement is examined when one of the three parties moves
with a uniform acceleration with respect to other parties. As Unruh effect
indicates, the tripartite entanglement exhibits a decreasing behavior with
increasing the acceleration. Unlike the bipartite entanglement, however, the
tripartite entanglement does not completely vanish in the infinite acceleration
limit. If the three parties, for example, share the Greenberger-Horne-Zeilinger
or W-state initially, the corresponding -tangle, one of the measures for
tripartite entanglement, is shown to be or 0.176 in this
limit, respectively. This fact indicates that the tripartite quantum
information processing may be possible even if one of the parties approaches to
the Rindler horizon. The physical implications of this striking result are
discussed in the context of black hole physics.Comment: 19 pages, 5 figure
Demon-free quantum Brownian motors
A quantum Smoluchowski equation is put forward that consistently describes
thermal quantum states. In particular, it notably does not induce a violation
of the second law of thermodynamics. This so modified kinetic equation is
applied to study {\it analytically} directed quantum transport at strong
friction in arbitrarily shaped ratchet potentials that are driven by nonthermal
two-state noise. Depending on the mutual interplay of quantum tunneling and
quantum reflection these quantum corrections can induce both, either a sizable
enhancement or a suppression of transport. Moreover, the threshold for current
reversals becomes markedly shifted due to such quantum fluctuations.Comment: 4 pages 3 figure
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