599 research outputs found
Collective Atomic Motion in an Optical Lattice formed inside a High Finesse Cavity
We report on collective non-linear dynamics in an optical lattice formed
inside a high finesse ring cavity in a so far unexplored regime, where the
light shift per photon times the number of trapped atoms exceeds the cavity
resonance linewidth. We observe bistability and self-induced squeezing
oscillations resulting from the retro-action of the atoms upon the optical
potential wells. We can well understand most of our observations within a
simplified model assuming adiabaticity of the atomic motion. Non-adiabatic
aspects of the atomic motion are reproduced by solving the complete system of
coupled non-linear equations of motion for hundred atoms.Comment: 4 pages, 5 figure
Group Representation for the Working Class? Opinion Differences among Occupational Groups in Germany
In this paper, we take up the burgeoning debate about the underrepresentation of the working class in politics. In the literature section we discuss theories of group representation and look at recent empirical studies of responsiveness that have begun to disaggregate public opinion by sociodemographic categories. Empirically, we analyze a dataset of more than 700 survey items collected in Germany between 1980 and 2012. The analysis shows that respondents within one social class are more similar to each other than to members of other classes and that class-based differences outweigh those of education, region, or gender. While opinion differences are not always large, they can reach 50 percentage points. There are frequently gaps of between 20 or 30 percentage points in support for or opposition to policy changes. Since workers’ opinions tend to differ from the opinions of those groups who are well represented in parliament, their numerical underrepresentation might bias decisions against them, as recent studies suggest.In diesem Discussion Paper greifen wir die aktuelle Debatte über die politische Unterrepräsentation der Arbeiterklasse auf. Im Literaturteil stellen wir Kernargumente der Theorien deskriptiver Repräsentation dar und verknüpfen diese mit aktuellen Studien aus der empirischen Responsivitätsforschung. Im empirischen Abschnitt analysieren wir einen von uns erstellten Datensatz mit mehr als 700 Sachfragen, die jeweils nach der Zustimmung oder Ablehnung einer vorgeschlagenen Politikänderung fragen. Die Sachfragen stammen aus Umfragen, die zwischen 1980 und 2012 erhoben wurden. Wir zeigen, dass sich die Befragten innerhalb einer sozialen Klasse in ihren Einstellungen systematisch ähnlicher sind als Befragte aus unterschiedlichen sozialen Klassen. Zudem sind Einstellungsunterschiede zwischen sozialen Klassen größer als zwischen anderen sozialen Gruppen (Bildung, Region, Geschlecht); sie betragen häufig mehr als 20 oder 30 Prozentpunkte. Da Arbeiter sich von den Gruppen unterscheiden, die zahlenmäßig stark im Parlament vertreten sind, könnte dies vermehrt zu Politikentscheidungen entgegen ihren Interessen führen.1 Introduction 2 Social class 3 Theory and literature review The theoretical case for group representation Inequality and responsiveness: Empirical studies 4 Data and methods 5 Empirical analysis 6 Conclusion Reference
Effects of sublattice symmetry and frustration on ionic transport in garnet solid electrolytes
We use rigorous group-theoretic techniques and molecular dynamics to
investigate the connection between structural symmetry and ionic conductivity
in the garnet family of solid Li-ion electrolytes. We identify new ordered
phases and order-disorder phase transitions that are relevant for conductivity
optimization. Ionic transport in this materials family is controlled by the
frustration of the Li sublattice caused by incommensurability with the host
structure at non-integer Li concentrations, while ordered phases explain
regions of sharply lower conductivity. Disorder is therefore predicted to be
optimal for ionic transport in this and other conductor families with strong Li
interaction.Comment: 6 pages, 4 figures, and supplementary informatio
The prismatic Sigma 3 (10-10) twin bounday in alpha-Al2O3 investigated by density functional theory and transmission electron microscopy
The microscopic structure of a prismatic twin
boundary in \aal2o3 is characterized theoretically by ab-initio
local-density-functional theory, and experimentally by spatial-resolution
electron energy-loss spectroscopy in a scanning transmission electron
microscope (STEM), measuring energy-loss near-edge structures (ELNES) of the
oxygen -ionization edge. Theoretically, two distinct microscopic variants
for this twin interface with low interface energies are derived and analysed.
Experimentally, it is demonstrated that the spatial and energetical resolutions
of present high-performance STEM instruments are insufficient to discriminate
the subtle differences of the two proposed interface variants. It is predicted
that for the currently developed next generation of analytical electron
microscopes the prismatic twin interface will provide a promising benchmark
case to demonstrate the achievement of ELNES with spatial resolution of
individual atom columns
Patterns of cytokines and lymphocyte subsets in patients with breast and prostate cancer treated with a standardized mistletoe extract preparation
Parallel Search with no Coordination
We consider a parallel version of a classical Bayesian search problem.
agents are looking for a treasure that is placed in one of the boxes indexed by
according to a known distribution . The aim is to minimize
the expected time until the first agent finds it. Searchers run in parallel
where at each time step each searcher can "peek" into a box. A basic family of
algorithms which are inherently robust is \emph{non-coordinating} algorithms.
Such algorithms act independently at each searcher, differing only by their
probabilistic choices. We are interested in the price incurred by employing
such algorithms when compared with the case of full coordination. We first show
that there exists a non-coordination algorithm, that knowing only the relative
likelihood of boxes according to , has expected running time of at most
, where is the expected running time of the best
fully coordinated algorithm. This result is obtained by applying a refined
version of the main algorithm suggested by Fraigniaud, Korman and Rodeh in
STOC'16, which was designed for the context of linear parallel search.We then
describe an optimal non-coordinating algorithm for the case where the
distribution is known. The running time of this algorithm is difficult to
analyse in general, but we calculate it for several examples. In the case where
is uniform over a finite set of boxes, then the algorithm just checks boxes
uniformly at random among all non-checked boxes and is essentially times
worse than the coordinating algorithm.We also show simple algorithms for Pareto
distributions over boxes. That is, in the case where for
, we suggest the following algorithm: at step choose uniformly
from the boxes unchecked in ,
where . It turns out this algorithm is asymptotically
optimal, and runs about times worse than the case of full coordination
First-principles analysis of the interplay between electronic structure and volume change in colquiriite compounds during Li intercalation
A main source of capacity fading in lithium-ion batteries is the degradation
of the active cathode materials caused by the series of volume changes during
charge and discharge cycles. The quaternary colquiriite-type fluorides
LiCaFeF and LiCaCoF were reported to have
negligible volume changes in specific Li concentration ranges, making the
underlying colquiriite structure a promising candidate for so-called
zero-strain behavior. Using first-principles electronic structure calculations
based on density functional theory with a Hubbard- correlation correction on
the transition-metal ions, we systematically investigate the equilibrium
volumes of the colquiriite-type fluorides LiCaMF with M =Ti,
V, Cr, Mn, Fe, Co, and Ni at the Li concentrations =0, 1, and 2. We
elucidate the connection between the total volume of the structures and the
local volumes of fluorine coordinated octahedra around the cations, and we find
trends along the series of the 3d transition-metal elements. In the lithiation
step from =1 to =2 we find volume changes of about 10 %, and we discuss
the discrepancy to the experimentally reported smaller value for
LiCaFeF. From =0 to =1 we describe the compensating
structural mechanisms that lead to an exceptionally small volume change of
LiCaMnF. This compound is therefore a particularly promising
zero-strain cathode material.Comment: 13 pages, 9 Figure
A new Determination of the Extragalactic Background of Diffuse Gamma Rays taking into account Dark Matter Annihilation
The extragalactic background (EGB) of diffuse gamma rays can be determined by
subtracting the Galactic contribution from the data. This requires a Galactic
model (GM) and we include for the first time the contribution of dark matter
annihilation (DMA), which was previously proposed as an explanation for the
EGRET excess of diffuse Galactic gamma rays above 1 GeV.
In this paper it is shown that the newly determined EGB shows a
characteristic high energy bump on top of a steeply falling soft contribution.
The bump is shown to be compatible with a contribution from an extragalactic
DMA signal from weakly interacting massive particles (WIMPs) with a mass
between 50 and 100 GeV in agreement with the EGRET excess of the Galactic
diffuse gamma rays and in disagreement with earlier analysis. The remaining
soft contribution of the EGB is shown to resemble the spectra of the observed
point sources in our Galaxy.Comment: 7 pages, 4 figures. Accepted by A&A, made Fig. 4 and table 1
consisten
- …