29,608 research outputs found
Baffling of fluid sloshing in cylindrical tanks Final report
Annular baffle for damping liquid oscillations in partially filled cylindrical tan
Testing Higher-Order Lagrangian Perturbation Theory Against Numerical Simulations - 1. Pancake Models
We present results showing an improvement of the accuracy of perturbation
theory as applied to cosmological structure formation for a useful range of
quasilinear scales. The Lagrangian theory of gravitational instability of an
Einstein-de Sitter dust cosmogony investigated and solved up to the third order
in the series of papers by Buchert (1989, 1992, 1993a), Buchert \& Ehlers
(1993), Buchert (1993b), Ehlers \& Buchert (1993), is compared with numerical
simulations. In this paper we study the dynamics of pancake models as a first
step. In previous work (Coles \etal 1993, Melott \etal 1993, Melott 1993) the
accuracy of several analytical approximations for the modeling of large-scale
structure in the mildly non-linear regime was analyzed in the same way,
allowing for direct comparison of the accuracy of various approximations. In
particular, the ``Zel'dovich approximation'' (Zel'dovich 1970, 1973, hereafter
ZA) as a subclass of the first-order Lagrangian perturbation solutions was
found to provide an excellent approximation to the density field in the mildly
non-linear regime (i.e. up to a linear r.m.s. density contrast of ). The performance of ZA in hierarchical clustering models can be
greatly improved by truncating the initial power spectrum (smoothing the
initial data). We here explore whether this approximation can be further
improved with higher-order corrections in the displacement mapping from
homogeneity. We study a single pancake model (truncated power-spectrum with
power-index ) using cross-correlation statistics employed inComment: TeX, 18 pages excl.figures; contact [email protected] ;
[email protected] . submitted to Astron. & Astrophy
Identification of Coulomb blockade and macroscopic quantum tunneling by noise
The effects of Macroscopic Quantum Tunneling (MQT) and Coulomb Blockade (CB)
in Josephson junctions are of considerable significance both for the
manifestations of quantum mechanics on the macroscopic scale and potential
technological applications. These two complementary effects are shown to be
clearly distinguishable from the associated noise spectra. The current noise is
determined exactly and a rather sharp crossover between flux noise in the MQT
and charge noise in the CB regions is found as the applied voltage is changed.
Related results hold for the voltage noise in current-biased junctions.Comment: 6 pages, 3 figures, epl.cls include
Scaling and data collapse for the mean exit time of asset prices
We study theoretical and empirical aspects of the mean exit time of financial
time series. The theoretical modeling is done within the framework of
continuous time random walk. We empirically verify that the mean exit time
follows a quadratic scaling law and it has associated a pre-factor which is
specific to the analyzed stock. We perform a series of statistical tests to
determine which kind of correlation are responsible for this specificity. The
main contribution is associated with the autocorrelation property of stock
returns. We introduce and solve analytically both a two-state and a three-state
Markov chain models. The analytical results obtained with the two-state Markov
chain model allows us to obtain a data collapse of the 20 measured MET profiles
in a single master curve.Comment: REVTeX 4, 11 pages, 8 figures, 1 table, submitted for publicatio
Implications of policy framework conditions for the development of forestry-based social innovation initiatives in Slovenia
Non-Markov dynamics and phonon decoherence of a double quantum dot charge qubit
In this paper we investigate decoherence times of a double quantum dot (DQD)
charge qubit due to it coupling with acoustic phonon baths. We individually
consider the acoustic piezoelectric as well as deformation coupling phonon
baths in the qubit environment. The decoherence times are calculated with two
kinds of methods. One of them is based on the qusiadiabatic propagator path
integral (QUAPI) and the other is based on Bloch equations, and two kinds of
results are compared. It is shown that the theoretical decoherence times of the
DQD charge qubit are shorter than the experimental reported results. It implies
that the phonon couplings to the qubit play a subordinate role, resulting in
the decoherence of the qubit.Comment: 5 pages, 4 figure
Signatures of a Noise-Induced Quantum Phase Transition in a Mesoscopic Metal Ring
We study a mesoscopic ring with an in-line quantum dot threaded by an
Aharonov-Bohm flux. Zero-point fluctuations of the electromagnetic environment
capacitively coupled to the ring, with spectral density, can
suppress tunneling through the dot, resulting in a quantum phase transition
from an unpolarized to a polarized phase. We show that robust signatures of
such a transition can be found in the response of the persistent current in the
ring to the external flux as well as to the bias between the dot and the arm.
Particular attention is paid to the experimentally relevant cases of ohmic
() and subohmic () noise.Comment: 4 pages, 4 figures, realistic parameters estimated, reference update
Diffusive behavior of a greedy traveling salesman
Using Monte Carlo simulations we examine the diffusive properties of the
greedy algorithm in the d-dimensional traveling salesman problem. Our results
show that for d=3 and 4 the average squared distance from the origin is
proportional to the number of steps t. In the d=2 case such a scaling is
modified with some logarithmic corrections, which might suggest that d=2 is the
critical dimension of the problem. The distribution of lengths also shows
marked differences between d=2 and d>2 versions. A simple strategy adopted by
the salesman might resemble strategies chosen by some foraging and hunting
animals, for which anomalous diffusive behavior has recently been reported and
interpreted in terms of Levy flights. Our results suggest that broad and
Levy-like distributions in such systems might appear due to dimension-dependent
properties of a search space.Comment: accepted in Phys. Rev.
Tangential Touch between the Free and the Fixed Boundary in a Semilinear Free Boundary Problem in Two Dimensions
The main result of this paper concerns the behavior of a free boundary
arising from a minimization problem, close to the fixed boundary in two
dimensions
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