7,933 research outputs found
CPT Violation Implies Violation of Lorentz Invariance
An interacting theory that violates CPT invariance necessarily violates
Lorentz invariance. On the other hand, CPT invariance is not sufficient for
out-of-cone Lorentz invariance. Theories that violate CPT by having different
particle and antiparticle masses must be nonlocal.Comment: Minor changes in the published versio
Complete methods set for scalable ion trap quantum information processing
Large-scale quantum information processors must be able to transport and
maintain quantum information, and repeatedly perform logical operations. Here
we demonstrate a combination of all the fundamental elements required to
perform scalable quantum computing using qubits stored in the internal states
of trapped atomic ions. We quantify the repeatability of a multi-qubit
operation, observing no loss of performance despite qubit transport over
macroscopic distances. Key to these results is the use of different pairs of
beryllium ion hyperfine states for robust qubit storage, readout and gates, and
simultaneous trapping of magnesium re-cooling ions along with the qubit ions.Comment: 9 pages, 4 figures. Accepted to Science, and thus subject to a press
embarg
Surface charging of thick porous water ice layers relevant for ion sputtering experiments
We use a laboratory facility to study the sputtering properties of
centimeter-thick porous water ice subjected to the bombardment of ions and
electrons to better understand the formation of exospheres of the icy moons of
Jupiter. Our ice samples are as similar as possible to the expected moon
surfaces but surface charging of the samples during ion irradiation may distort
the experimental results. We therefore monitor the time scales for charging and
dis- charging of the samples when subjected to a beam of ions. These
experiments allow us to derive an electric conductivity of deep porous ice
layers. The results imply that electron irradiation and sputtering play a
non-negligible role for certain plasma conditions at the icy moons of Jupiter.
The observed ion sputtering yields from our ice samples are similar to previous
experiments where compact ice films were sputtered off a micro-balance.Comment: arXiv admin note: text overlap with arXiv:1509.0400
P.A.M. Dirac and the Discovery of Quantum Mechanics
Dirac's contributions to the discovery of non-relativistic quantum mechanics
and quantum electrodynamics, prior to his discovery of the relativistic wave
equation, are described
Euclidean versus hyperbolic congestion in idealized versus experimental networks
This paper proposes a mathematical justification of the phenomenon of extreme
congestion at a very limited number of nodes in very large networks. It is
argued that this phenomenon occurs as a combination of the negative curvature
property of the network together with minimum length routing. More
specifically, it is shown that, in a large n-dimensional hyperbolic ball B of
radius R viewed as a roughly similar model of a Gromov hyperbolic network, the
proportion of traffic paths transiting through a small ball near the center is
independent of the radius R whereas, in a Euclidean ball, the same proportion
scales as 1/R^{n-1}. This discrepancy persists for the traffic load, which at
the center of the hyperbolic ball scales as the square of the volume, whereas
the same traffic load scales as the volume to the power (n+1)/n in the
Euclidean ball. This provides a theoretical justification of the experimental
exponent discrepancy observed by Narayan and Saniee between traffic loads in
Gromov-hyperbolic networks from the Rocketfuel data base and synthetic
Euclidean lattice networks. It is further conjectured that for networks that do
not enjoy the obvious symmetry of hyperbolic and Euclidean balls, the point of
maximum traffic is near the center of mass of the network.Comment: 23 pages, 4 figure
Spectral plots and the representation and interpretation of biological data
It is basic question in biology and other fields to identify the char-
acteristic properties that on one hand are shared by structures from a
particular realm, like gene regulation, protein-protein interaction or neu- ral
networks or foodwebs, and that on the other hand distinguish them from other
structures. We introduce and apply a general method, based on the spectrum of
the normalized graph Laplacian, that yields repre- sentations, the spectral
plots, that allow us to find and visualize such properties systematically. We
present such visualizations for a wide range of biological networks and compare
them with those for networks derived from theoretical schemes. The differences
that we find are quite striking and suggest that the search for universal
properties of biological networks should be complemented by an understanding of
more specific features of biological organization principles at different
scales.Comment: 15 pages, 7 figure
Magneto Seebeck effect in REFeAsO (RE=rare earth) compounds: probing the magnon drag scenario
We investigate Seebeck effect in REFeAsO (RE=rare earth)compounds as a
function of temperature and magnetic field up to 30T. The Seebeck curves are
characterized by a broad negative bump around 50K, which is sample dependent
and strongly enhanced by the application of a magnetic field. A model for the
temperature and field dependence of the magnon drag contribution to the Seebeck
effect by antiferromagnetic (AFM) spin fluctuation is developed. It accounts
for the magnitude and scaling properties of such bump feature in our
experimental data. This analysis allows to extract precious information on the
coupling between electrons and AFM spin fluctuations in these parent compound
systems, with implications on the pairing mechanism of the related
superconducting compounds
Spectral Properties and Synchronization in Coupled Map Lattices
Spectral properties of Coupled Map Lattices are described. Conditions for the
stability of spatially homogeneous chaotic solutions are derived using linear
stability analysis. Global stability analysis results are also presented. The
analytical results are supplemented with numerical examples. The quadratic map
is used for the site dynamics with different coupling schemes such as global
coupling, nearest neighbor coupling, intermediate range coupling, random
coupling, small world coupling and scale free coupling.Comment: 10 pages with 15 figures (Postscript), REVTEX format. To appear in
PR
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