1,625,534 research outputs found
EPR-entangled Bose-Einstein condensates in state-dependent potentials: a dynamical study
We study generation of non-local correlations by atomic interactions in a
pair of bi-modal Bose-Einstein Condensates in state-dependent potentials
including spatial dynamics. The wave-functions of the four components are
described by combining a Fock state expansion with a time-dependent
Hartree-Fock Ansatz, so that both the spatial dynamics and the local and
non-local quantum correlations are accounted for. We find that despite the
spatial dynamics, our protocole generates enough non-local entanglement to
perform an EPR steering experiment with two spatially separated con-densates of
a few thousands of atoms
Efficient Estimation of an Additive Quantile Regression Model
In this paper two kernel-based nonparametric estimators are proposed for estimating the components of an additive quantile regression model. The first estimator is a computationally convenient approach which can be viewed as a viable alternative to the method of De Gooijer and Zerom (2003). With the aim to reduce variance of the first estimator, a second estimator is defined via sequential fitting of univariate local polynomial quantile smoothing for each additive component with the other additive components replaced by the corresponding estimates from the first estimator. The second estimator achieves oracle efficiency in the sense that each estimated additive component has the same variance as in the case when all other additive components were known. Asymptotic properties are derived for both estimators under dependent processes that are strictly stationary and absolutely regular. We also provide a demonstrative empirical application of additive quantile models to ambulance travel times.Additive models; Asymptotic properties; Dependent data; Internalized kernel smoothing; Local polynomial; Oracle efficiency
Time-dependent Kohn-Sham theory with memory
In time-dependent density-functional theory, exchange and correlation (xc)
beyond the adiabatic local density approximation can be described in terms of
viscoelastic stresses in the electron liquid. In the time domain, this leads to
a velocity-dependent xc vector potential with a memory containing short- and
long-range components. The resulting time-dependent Kohn-Sham formalism
describes the dynamics of electronic systems including decoherence and
relaxation. For the example of collective charge-density oscillations in a
quantum well, we illustrate the xc memory effects, clarify the dissipation
mechanism, and extract intersubband relaxation rates for weak and strong
excitations.Comment: 4 pages, 4 figure
Scale-Dependent Non-Gaussianity as a Generalization of the Local Model
We generalize the local model of primordial non-Gaussianity by promoting the
parameter fNL to a general scale-dependent function fNL(k). We calculate the
resulting bispectrum and the effect on the bias of dark matter halos, and thus
the extent to which fNL(k) can be measured from the large-scale structure
observations. By calculating the principal components of fNL(k), we identify
scales where this form of non-Gaussianity is best constrained and estimate the
overlap with previously studied local and equilateral non-Gaussian models.Comment: Accepted to JCAP. 22 pages, 4 figure
Density-based crystal plasticity : from the discrete to the continuum
Because of the enormous range of time and space scales involved in
dislocation dynamics, plastic modeling at macroscale requires a continuous
formulation. In this paper, we present a rigorous formulation of the transition
between the discrete, where plastic flow is resolved at the scale of individual
dislocations, and the continuum, where dislocations are represented by
densities. First, we focus on the underlying coarse-graining procedure and show
that the emerging correlation-induced stresses are scale-dependent. Each of
these stresses can be expanded into the sum of two components. The first one
depends on the local values of the dislocation densities and always opposes the
sum of the applied stress and long-range mean field stress generated by the
geometrically necessary dislocation (GND) density; this stress acts as a
friction stress. The second component depends on the local gradients of the
dislocation densities and is inherently associated to a translation of the
elastic domain; therefore, it acts as a back-stress. We also show that these
friction and back- stresses contain symmetry-breaking components that make the
local stress experienced by dislocations to depend on the sign of their Burgers
vector
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