10,395 research outputs found
The labour market after age 50: some elements of a Franco-American comparison
This paper examines various supply and demand side aspects of the French labour market for older workers and puts them in perspective by comparing them to the US case. We first consider the supply side incentives (or disincentives) of basic pension schemes for the two countries : for France, we discuss how these incentives have been changed by the 1993 and 2003 pension reforms and we present some projections of the impact of these reforms on labour force participation rates, based on the DESTINIE dynamic microsimulation model. We then discuss, on the demand side, the hypothesis of a wage-productivity gap for older workers which could explain their lower employment rates. Evidence in favor of this hypothesis is not overwhelming. Nevertheless, workers who lose their jobs at older ages probably suffer a large loss of firm-specific and sector-specific human capital. In the US, this does not preclude re-employment, but at the cost of significant drops of wage levels. In France, the collective choice has been made since the 1970s to allow older workers who lose their jobs to completely withdraw from the labour market : these workers have access to preretirement schemes or specific dispositions of unemployment insurance (including an exemption from seeking employment). This system proved difficult to regulate. Due to these difficulties, France has not been able to do more than stabilize the employment rate in the 55-64 age bracket during the 1990s, after 20 years of continuous decline. The key unanswered question is whether it will be possible to increase the employment rate of this age group in the next two decades.Pensions, preretirement, senior workers
BF Theories and Group-Level Duality
It is known that the partition function and correlators of the
two-dimensional topological field theory on the Riemann
surface is given by Verlinde numbers, dim() and that
the large limit of dim() gives Vol(), the volume of
the moduli space of flat connections of gauge group on ,
up to a power of . Given this relationship, we complete the computation of
Vol() using only algebraic results from conformal field theory. The
group-level duality of is used to show that if is a classical
group, then is a BF
theory with gauge group . Therefore this limit computes Vol(), the volume of the moduli space of flat connections of gauge
group
Penrose Limits and Spacetime Singularities
We give a covariant characterisation of the Penrose plane wave limit: the
plane wave profile matrix is the restriction of the null geodesic
deviation matrix (curvature tensor) of the original spacetime metric to the
null geodesic, evaluated in a comoving frame. We also consider the Penrose
limits of spacetime singularities and show that for a large class of black
hole, cosmological and null singularities (of Szekeres-Iyer ``power-law
type''), including those of the FRW and Schwarzschild metrics, the result is a
singular homogeneous plane wave with profile , the scale
invariance of the latter reflecting the power-law behaviour of the
singularities.Comment: 9 pages, LaTeX2e; v2: additional references and cosmetic correction
Lorentzian homogeneous spaces admitting a homogeneous structure of type T1+T3
We show that a Lorentzian homogeneous space admitting a homogeneous structure
of type T1 + T3 is either a (locally) symmetric space or a singular homogeneous
plane wave.Comment: 7 pages, Latex2e, a small note and a reference adde
Boundary fermion currents and subleading order chiral anomaly in the AdS/CFT correspondence
We construct a wave-functional whose argument couples to boundary fermion
currents in the AdS/CFT correspondence. Using this we calculate the
contributions from bulk fermions to the chiral anomaly that give the subleading
order term in the exact -dependence of the chiral anomaly of
SYM. The result agrees with the calculation of Bilal & Chu.Comment: 6 page
PP-wave and Non-supersymmetric Gauge Theory
We extend the pp-wave correspondence to a non supersymmetric example. The
model is the type 0B string theory on the pp-wave R-R background. We explicitly
solve the model and give the spectrum of physical states. The field theory
counterpart is given by a sector of the large N SU(N) x SU(N) CFT living on a
stack of N electric and N magnetic D3-branes. The relevant effective coupling
constant is g_{eff}=g_sN/J^2. The string theory has a tachyon in the spectrum,
whose light-cone energy can be exactly computed as a function of g_{eff}. We
argue that the perturbative analysis in g_{eff} in the dual gauge theory is
reliable, with corrections of non perturbative type. We find a precise
state/operator map, showing that the first perturbative corrections to the
anomalous dimensions of the operators have the behavior expected from the
string analysis.Comment: 19 pages. Revised versio
Matrix string states in pure 2d Yang Mills theories
We quantize pure 2d Yang-Mills theory on a torus in the gauge where the field
strength is diagonal. Because of the topological obstructions to a global
smooth diagonalization, we find string-like states in the spectrum similar to
the ones introduced by various authors in Matrix string theory. We write
explicitly the partition function, which generalizes the one already known in
the literature, and we discuss the role of these states in preserving modular
invariance. Some speculations are presented about the interpretation of 2d
Yang-Mills theory as a Matrix string theory.Comment: Latex file of 38 pages plus 6 eps figures. A note and few references
added, figures improve
Self-replaceable thermocouple for molten steel bath - A concept
Thermocouple wires, consisting of tungsten-rhenium alloy protected by ablative ceramic coating, are wound on a reel and fed continuously into bath. Tests indicate accuracy and reliability are comparable to conventional devices
Generalized two-dimensional Yang-Mills theory is a matrix string theory
We consider two-dimensional Yang-Mills theories on arbitrary Riemann
surfaces. We introduce a generalized Yang-Mills action, which coincides with
the ordinary one on flat surfaces but differs from it in its coupling to
two-dimensional gravity. The quantization of this theory in the unitary gauge
can be consistently performed taking into account all the topological sectors
arising from the gauge-fixing procedure. The resulting theory is naturally
interpreted as a Matrix String Theory, that is as a theory of covering maps
from a two-dimensional world-sheet to the target Riemann surface.Comment: LaTeX, 10 pages, uses espcrc2.sty. Presented by A. D'adda at the
Third Meeting on Constrained Dynamics and Quantum Gravity, Villasimius
(Sardinia, Italy) September 13-17, 1999; to appear in the proceeding
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