3,042 research outputs found
Dispersion for the wave equation inside strictly convex domains I: the Friedlander model case
We consider a model case for a strictly convex domain of dimension
with smooth boundary and we describe dispersion for the wave equation with
Dirichlet boundary conditions. More specifically, we obtain the optimal fixed
time decay rate for the smoothed out Green function: a loss occurs
with respect to the boundary less case, due to repeated occurrences of
swallowtail type singularities in the wave front set.Comment: 53 pages, 4 figures, to appear in Annals of Math. Fixed typos, added
remark
Worker flows, job flows and establishment wage differentials : analyzing the case of France
We address the relation between establishment wage differentials and worker flows, i.e. the churning rate and the quit rate. Our analysis is based on a linked employer-employee dataset covering the French private non-farm sector from 2002 to 2005. Our estimations support the hypothesis that wage premium is an efficient human resource management tool to stabilize workers : churning rates are lower in high-paying firms due to lower quit rates. We further show that the relation is not linear, and it differs among skill groups and according to establishment size : it is strongest for low-wage levels, for low-skilled workers and in large establishments.Establishment wage effects, worker flows, churning rate, quite rate, linked employer-employee panel data, France.
Manipulation of edge states in microwave artificial graphene
Edge states are one important ingredient to understand transport properties
of graphene nanoribbons. We study experimentally the existence and the internal
structure of edge states under uniaxial strain of the three main edges: zigzag,
bearded, and armchair. The experiments are performed on artificial microwave
graphene flakes, where the wavefunctions are obtained by direct imaging. We
show that uniaxial strain can be used to manipulate the edge states: a single
parameter controls their existence and their spatial extension into the ribbon.
By combining tight-binding approach and topological arguments, we provide an
accurate description of our experimental findings. A new type of zero-energy
state appearing at the intersection of two edges, namely the corner state, is
also observed and discussed.Comment: 15 pages, 9 figure
Tight-binding couplings in microwave artificial graphene
We experimentally study the propagation of microwaves in an artificial
honeycomb lattice made of dielectric resonators. This evanescent propagation is
well described by a tight-binding model, very much like the propagation of
electrons in graphene. We measure the density of states, as well as the wave
function associated with each eigenfrequency. By changing the distance between
the resonators, it is possible to modulate the amplitude of
next-(next-)nearest-neighbor hopping parameters and to study their effect on
the density of states. The main effect is the density of states becoming
dissymmetric and a shift of the energy of the Dirac points. We study the basic
elements: An isolated resonator, a two-level system, and a square lattice. Our
observations are in good agreement with analytical solutions for corresponding
infinite lattice.Comment: 10 pages, 9 figure
Topological transition of Dirac points in a microwave experiment
By means of a microwave tight-binding analogue experiment of a graphene-like
lattice, we observe a topological transition between a phase with a point-like
band gap characteristic of massless Dirac fermions and a gapped phase. By
applying a controlled anisotropy on the structure, we investigate the
transition directly via density of states measurements. The wave function
associated with each eigenvalue is mapped and reveals new states at the Dirac
point, localized on the armchair edges. We find that with increasing
anisotropy, these new states are more and more localized at the edges.Comment: Physical Review Letters (2013) XX
The effect of social security payroll tax reductions on employment and wages: an evaluation of the 2003 French reform
public policy evaluation, payroll tax cuts, labour cost, semi-parametric estimations
An evaluation of the impact of industrial restructuring on individual human capital accumulation in France (1956-1993)
This article evaluates the effect of French industrial restructuring during 1956-1993, on individual human capital accumulation. We use data from the French Training and Occupational Skills survey and the Population Census (INSEE). We estimate a human capital production function using two econometric strategies (controlling for covariates; instrumental variables). We show that industrial restructuring has a negative impact on individual human capital accumulation for the children of blue-collar workers
Payroll tax reductions and job flows in France
In France, policies that aim at reducing labour cost have extended to more and more workers since the beginning of the 90s. Evaluations of the effect of payroll tax reduction often use estimations of labour demand equations. In this paper, we consider the impact of labour tax cuts on job creations and destructions through the Fillon reform (2003), by using a fixed effect instrumental variable approach and a sectora l pseudo panel dataset. Over 2002-2005, our estimates show that PTR let job flows unchanged
New counterexamples to Strichartz estimates for the wave equation on a 2d model convex domain
We prove that the range of Strichartz estimates on a model 2D convex domain
may be further restricted compared to the known counterexamples due to the
first author. Our new family of counterexamples is now built on the parametrix
construction from our earlier work. Interestingly enough, it is sharp in at
least some regions of phase space.Comment: 23 pages, 1 figur
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