36,978 research outputs found
Energy consumption for ion transport in a segmented Paul trap
There is recent interest in determining energy costs of shortcuts to
adiabaticity (STA), but different definitions of "cost" have been used. We
demonstrate the importance of taking into account the Control System (CS) for a
fair assessment of energy flows and consumptions. We model the energy
consumption and power to transport an ion by a STA protocol in a multisegmented
Paul trap. The ion is driven by an externally controlled, moving harmonic
oscillator. Even if no net ion- energy is gained at destination, setting the
time-dependent control parameters is a macroscopic operation that costs energy
and results in energy dissipation for the short time scales implied by the
intrinsically fast STA processes. The potential minimum is displaced by
modulating the voltages on control (dc) electrodes. A secondary effect of the
modulation, usually ignored as it does not affect the ion dynamics, is the
time- dependent energy shift of the potential minimum. The non trivial part of
the energy consumption is due to the electromotive forces to set the electrode
voltages through the low-pass filters required to preserve the electronic noise
from decohering the ion's motion. The results for the macroscopic CS (the Paul
trap) are compared to the microscopic power and energy of the ion alone.
Similarities are found -and may be used quantitatively to minimize costs- only
when the CS-dependent energy shift of the harmonic oscillator is included in
the ion energy
Ab initio calculations of structures and stabilities of (NaI)_nNa+ and (CsI)_nCs+ cluster ions
Ab initio calculations using the Perturbed Ion model, with correlation
contributions included, are presented for nonstoichiometric (NaI)_nNa+ and
(CsI)_nCs+ (n=1-14) cluster ions. The ground state and several low-lying
isomers are identified and described. Rocksalt ground states are common and
appear at cluster sizes lower than in the corresponding neutral systems. The
most salient features of the measured mobilities seem to be explained by
arguments related to the changes of the compactness of the clusters as a
function of size. The stability of the cluster ions against evaporation of a
single alkali halide molecule shows variations that explain the enhanced
stabilities found experimentally for cluster sizes n=4, 6, 9, and 13. Finally,
the ionization energies and the orbital eigenvalue spectrum of two (NaI)_13Na+
isomers are calculated and shown to be a fingerprint of the structure.Comment: 8 pages plus 13 postscript figures, LaTeX. Accepted for publication
in Phys, Rev. B; minor changes including a more complete comparison to pair
potential result
One-dimensional solitary waves in singular deformations of SO(2) invariant two-component scalar field theory models
In this paper we study the structure of the manifold of solitary waves in
some deformations of SO(2) symmetric two-component scalar field theoretical
models in two-dimensional Minkowski space. The deformation is chosen in order
to make the analogous mechanical system Hamilton-Jacobi separable in polar
coordinates and displays a singularity at the origin of the internal plane. The
existence of the singularity confers interesting and intriguing properties to
the solitary waves or kink solutions.Comment: 25 pages, 18 figure
Time relaxation of interacting single--molecule magnets
We study the relaxation of interacting single--molecule magnets (SMMs) in
both spatially ordered and disordered systems. The tunneling window is assumed
to be, as in Fe8, much narrower than the dipolar field spread. We show that
relaxation in disordered systems differs qualitatively from relaxation in fully
occupied cubic and Fe_8 lattices. We also study how line shapes that develop in
''hole--digging'' experiments evolve with time t in these fully occupied
lattices. We show (1) that the dipolar field h scales as t^p in these hole line
shapes and show (2) how p varies with lattice structure. Line shapes are not,
in general, Lorentzian. More specifically, in the lower portion of the hole,
they behave as (h/t^p)^{(1/p)-1} if h is outside the tunnel window. This is in
agreement with experiment and with our own Monte Carlo results.Comment: 21 LaTeX pages, 6 eps figures. Submitted to PRB on 15 June 2005.
Accepted on 13 August 200
Chiral low-energy constants from tau data
We analyze how the recent precise hadronic tau-decay data on the V-A spectral
function and general properties of QCD such as analyticity, the operator
product expansion and chiral perturbation theory (ChPT), can be used to improve
the knowledge of some of the low-energy constants of ChPT. In particular we
find the most precise values of L_{9,10} (or equivalently l_{5,6}) at order p^4
and p^6 and the first phenomenological determination of C_87 (c_50).Comment: Proceedings of the 6th International Workshop on Chiral Dynamics
(Bern, Switzerland, July 6-10, 2009). 9 pages, 3 figure
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