170,642 research outputs found
Dynamics of a two-level system under the simultaneous influence of a spin bath and a boson bath
We study dynamics of a two-level system coupled simultaneously to a pair of
dissimilar reservoirs, namely, a spin bath and a boson bath, which are
connected via finite interbath coupling. It is found that the steady-state
energy transfer in the two-level system increases with its coupling to the spin
bath while optimal transfer occurs at intermediate coupling in the transient
process. If the two-level system is strongly coupled to the spin bath, the
population transfer is unidirectional barring minor population oscillations of
minute amplitudes. If the spin bath is viewed as an atomic ensemble, robust
generation of macroscopic superposition states exists against parameter
variations of the two-level system and the boson bath.Comment: 12 pages, 4 figure
Gravity-mediated holography in fluid dynamics
For any spherically symmetric black hole spacetime with an ideal fluid
source, we establish a dual fluid system on a hypersurface near the black hole
horizon. The dual fluid is incompressible and obeys Navier-Stokes equation
subject to some external force. The force term in the fluid equation consists
in two parts, one comes from the curvature of the hypersurface, the other comes
from the stress-energy of the bulk fluid.Comment: 12 pages. v2: various corrections. v3: Minor corrections, version to
appear in Nucl. Phys.
Confidence bands in nonparametric time series regression
We consider nonparametric estimation of mean regression and conditional
variance (or volatility) functions in nonlinear stochastic regression models.
Simultaneous confidence bands are constructed and the coverage probabilities
are shown to be asymptotically correct. The imposed dependence structure allows
applications in many linear and nonlinear auto-regressive processes. The
results are applied to the S&P 500 Index data.Comment: Published in at http://dx.doi.org/10.1214/07-AOS533 the Annals of
Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical
Statistics (http://www.imstat.org
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