Gap between Lyapunov exponents for Hitchin representations

We study Lyapunov exponents for flat bundles over hyperbolic curves defined via parallel transport over the geodesic flow. We consider them as invariants on the space of Hitchin representations and show that there is a gap between any two consecutive Lyapunov exponents. Moreover we characterize the uniformizing representation of the Riemann surface as the one with the extremal gaps. The strategy of the proof is to relate Lyapunov exponents in the case of Anosov representations to other invariants, where the gap result is already available or where we can directly show it. In particular, firstly we relate Lyapunov exponents to a foliated Lyapunov exponent associated to a foliation H\"older isomorphic to the unstable foliation on the unitary tangent bundle of a Riemann surface. Secondly, we relate them to the renormalized intersection product in the setting of the thermodynamic formalism developed by Bridgeman, Canary, Labourie and Sambarino

Quelle incidence du CICE sur les salaires et l'emploi ? Une évaluation pour la période 2014-2017 t2 sur données de branches

Ce Working paper prolonge et actualise l'article de Ducoudré, Heyer et Plane (2015) qui analysait les premiers effets du Crédit d'Impôt pour la Compétitivité et l'Emploi (CICE) sur l'emploi et les salaires en utilisant des données trimestrielles par branche fournies par les comptes nationaux. Ce travail s’inscrit dans le débat sur l'évaluation du CICE récemment ravivé par les résultats du dernier rapport du comité de suivi de ce dispositif (France Stratégie, 2017) montrant qu'il n’y avait pas de consensus sur l'ampleur de ses effets sur l'économie française . Cette mesure, actuellement remise en cause par le nouvel exécutif, aurait, selon ce comité, un effet « difficile à déceler sur les salaires » et « positif mais modéré » sur l'emploi. Mais, les conclusions de ce rapport sont prudentes et appellent à prolonger et à multiplier les analyses de ce disposi

A 50-year high-resolution atmospheric reanalysis over France with the Safran system

Publié en ligne dans Wiley InterScience (www.interscience.wiley.com). Version auteur dans fichier pdf attaché.International audienceThe assessment of regional climate change requires the development of reference long-term retrospective meteorological datasets. This article presents an 8-km-resolution atmospheric reanalysis over France performed with the the Safran-gauge-based analysis system for the period 1958–2008. Climatological features of the Safran 50-year analysis – long-term mean values, inter-annual and seasonal variability – are first presented for all computed variables: rainfall, snowfall, mean air temperature, specific humidity, wind speed and solar and infrared radiation. The spatial patterns of precipitation, minimum and maximum temperature are compared with another spatialization method, and the temporal consistency of the reanalysis is assessed through various validation experiments with both dependent and independent data. These experiments demonstrate the overall robustness of the Safran reanalysis and the improvement of its quality with time, in connection with the sharp increase in the observation network density that occurred in the 1990s. They also show the differentiated sensitivity of variables to the number of available ground observations, with precipitation and air temperature being the more robust ones. The comparison of trends from the reanalysis with those from homogenized series finally shows that if spatial patterns are globally consistent with both approaches, care must be taken when using literal values from the reanalysis and corresponding statistical significance in climate change detection studies. The Safran 50-year atmospheric reanalysis constitutes a long-term forcing datasets for land surface schemes and thus enables the simulation of the past 50 years of water resources over France. Copyright © 2009 Royal Meteorological Societ

Multilevel and multiscale drought reanalysis over France with the Safran-Isba-Modcou hydrometeorological suite

Physically-based droughts can be defined as a water deficit in at least one component of the land surface hydrological cycle. The reliance of different activity domains (water supply, irrigation, hydropower, etc.) on specific components of this cycle requires drought monitoring to be based on indices related to meteorological, agricultural, and hydrological droughts. This paper describes a high-resolution retrospective analysis of such droughts in France over the last fifty years, based on the Safran-Isba-Modcou (SIM) hydrometeorological suite. The high-resolution 1958–2008 Safran atmospheric reanalysis was used to force the Isba land surface scheme and the hydrogeological model Modcou. Meteorological droughts are characterized with the Standardized Precipitation Index (SPI) at time scales varying from 1 to 24 months. Similar standardizing methods were applied to soil moisture and streamflow for identifying multiscale agricultural droughts – through the Standardized Soil Wetness Index (SSWI) – and multiscale hydrological droughts, through the Standardized Flow Index (SFI). Based on a common threshold level for all indices, drought event statistics over the 50-yr period – number of events, duration, severity and magnitude – have been derived locally in order to highlight regional differences at multiple time scales and at multiple levels of the hydrological cycle (precipitation, soil moisture, streamflow). Results show a substantial variety of temporal drought patterns over the country that are highly dependent on both the variable and time scale considered. Independent spatio-temporal drought events have then been identified and described by combining local characteristics with the evolution of area under drought. Summary statistics have finally been used to compare past severe drought events, from multi-year precipitation deficits (1989–1990) to short hot and dry periods (2003). Results show that the ranking of drought events depends highly on both the time scale and the variable considered. This multilevel and multiscale drought climatology will serve as a basis for assessing the impacts of climate change on droughts in France

The antinucleon-nucleon interaction at low energy : annihilation dynamics

The general properties of antiproton-proton annihilation at rest are presented, with special focus on the two-meson final states. The data exhibit remarkable dynamical selection rules : some allowed annihilation modes are suppressed by one order of magnitude with respect to modes of comparable phase-space. Various phenomenological analyses are reviewed, based on microscopic quark dynamics or symmetry considerations. The role of initial- and final-state interaction is also examined.Comment: 128 pages, 49 tables, 27 figure

The POINT-AGAPE Survey I: The Variable Stars in M31

The POINT-AGAPE collaboration has been monitoring M31 for three seasons with the Wide Field Camera on the Isaac Newton Telescope. In each season, data are taken for one hour per night for roughly sixty nights during the six months that M31 is visible. The two fields of view straddle the central bulge, northwards and southwards. We have calculated the locations, periods and amplitudes of 35414 variable stars in M31 as a by-product of our microlensing search. The variables are classified according to their period and amplitude of variation. They are classified into population I and II Cepheids, Miras and semi-regular long-period variables. The population I Cepheids are associated with the spiral arms, while the central concentration of the Miras and long-period variables varies noticeably, the stars with brighter (and shorter) variations being much more centrally concentrated. A crucial role in the microlensing experiment is played by the asymmetry signal. It was initially assumed that the variable stars would not be a serious problem as their distributions would be symmetric. We demonstrate that this assumption is not correct. We find that differential extinction associated with the dust lanes causes the variable star distributions to be asymmetric. The size and direction of the asymmetry of the variable stars is measured as a function of period and amplitude of variation. The implications of this discovery for the successful completion of the microlensing experiments towards M31 are discussed. (Abridged)Comment: To appear in MNRAS. Revised version including additional discussion on color of variables. Additional data table will be available once the paper is publishe