138,086 research outputs found
Labour Turnover and Firm Performance
We explore the impact of labour turnover on firm performance by analysing the predictions of an extension of the efficiency wage model of Salop (1979) developed by Garino and Martin (2007), which separates incumbent and newly hired workers in the production function. Within this theoretical framework, an exogenous increase in the turnover rate can increase profits if firms do not choose wages unilaterally. We test the theoretical predictions of the model using UK cross-section establishment-level data, the 2004 Workplace and Employee Relations Survey. In accordance with our theoretical priors, the empirical results support the standard inverse relationship between the quit rate and firm performance where firms unilaterally choose the wage and generally support a positive relationship between firm performance and the quit rate where trade unions influence wage setting
Amplitudes and Resonances from an Energy-Dependent Analysis of pbar+p -> pi+pi
The amplitudes at a series of discrete energies obtained from a previuos
analysis of pbar+p -> pi+pi have been used as input to a global energy-
dependent analysis of data in the momentum range 360 - 1550 MeV/c. The results
confirm the previous analysis and yield refined values for meson resonance
parameters in this energy region.Comment: 8 pages, LaTex, 2 postscript figures, a reference is correcte
Scaling universalities of kth-nearest neighbor distances on closed manifolds
Take N sites distributed randomly and uniformly on a smooth closed surface.
We express the expected distance from an arbitrary point on the
surface to its kth-nearest neighboring site, in terms of the function A(l)
giving the area of a disc of radius l about that point. We then find two
universalities. First, for a flat surface, where A(l)=\pi l^2, the k-dependence
and the N-dependence separate in . All kth-nearest neighbor distances
thus have the same scaling law in N. Second, for a curved surface, the average
\int d\mu over the surface is a topological invariant at leading and
subleading order in a large N expansion. The 1/N scaling series then depends,
up through O(1/N), only on the surface's topology and not on its precise shape.
We discuss the case of higher dimensions (d>2), and also interpret our results
using Regge calculus.Comment: 14 pages, 2 figures; submitted to Advances in Applied Mathematic
Cut Size Statistics of Graph Bisection Heuristics
We investigate the statistical properties of cut sizes generated by heuristic
algorithms which solve approximately the graph bisection problem. On an
ensemble of sparse random graphs, we find empirically that the distribution of
the cut sizes found by ``local'' algorithms becomes peaked as the number of
vertices in the graphs becomes large. Evidence is given that this distribution
tends towards a Gaussian whose mean and variance scales linearly with the
number of vertices of the graphs. Given the distribution of cut sizes
associated with each heuristic, we provide a ranking procedure which takes into
account both the quality of the solutions and the speed of the algorithms. This
procedure is demonstrated for a selection of local graph bisection heuristics.Comment: 17 pages, 5 figures, submitted to SIAM Journal on Optimization also
available at http://ipnweb.in2p3.fr/~martin
Orbital ordering promotes weakly-interacting S=1/2 dimers in the triangular lattice compound Sr3Cr2O8
The weakly interacting S=1/2 dimers system Sr3Cr2O8 has been investigated by
powder neutron diffraction and inelastic neutron scattering. Our data reveal a
structural phase transition below room temperature corresponding to an
antiferro-orbital ordering with nearly 90 degrees arrangement of the occupied
3z^2-r^2 d-orbital. This configuration leads to a drastic reduction of the
inter-dimer exchange energies with respect to the high temperature
orbital-disorder state, as shown by a spin-dimer analysis of the
super-superexchange interactions performed using the Extended Huckel Tight
Binding method. Inelastic neutron scattering reveals the presence of a quasi
non-dispersive magnetic excitation at 5.4 meV, in agreement with the picture of
weakly-interacting dimers
Phase behaviour of attractive and repulsive ramp fluids: integral equation and computer simulation studies
Using computer simulations and a thermodynamically self consistent integral
equation we investigate the phase behaviour and thermodynamic anomalies of a
fluid composed of spherical particles interacting via a two-scale ramp
potential (a hard core plus a repulsive and an attractive ramp) and the
corresponding purely repulsive model. Both simulation and integral equation
results predict a liquid-liquid de-mixing when attractive forces are present,
in addition to a gas-liquid transition. Furthermore, a fluid-solid transition
emerges in the neighbourhood of the liquid-liquid transition region, leading to
a phase diagram with a somewhat complicated topology. This solidification at
moderate densities is also present in the repulsive ramp fluid, thus preventing
fluid-fluid separation.Comment: 29 pages, 10 figure
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