Composantes irr\'eductibles de lieux sp\'eciaux d'espaces de modules de courbes, action galoisienne en genre quelconque

In this paper we characterise the action of the absolute Galois group on the geometric finite cyclic groups without \'etale factorization of stack inertia of the profinite geometric fundamental group of moduli spaces of marked curves. As a complementary result, we give the same action on prime order profinite elements in genus 2.Comment: in French, 26 pages, accepted for publication in "Annales de l'Institut Fourier", 2014 (64

From the bifurcation diagrams to the ease of playing of reed musical instruments. A theoretical illustration of the Bouasse-Benade prescription?

International audienceReed musical instruments can be described in terms of conceptually separate linear and nonlinear mechanisms: a localized nonlinear element (the valve effect due to the reed) excites a linear, passive acoustical multimode element (the musical instrument usually represented in the frequency domain by its input impedance). The linear element in turn influences the operation of the nonlinear element. The reed musical instruments are self-sustained oscillators. They generate an oscillating acoustical pressure (the note played) from a static over-pressure in the player's mouth (the blowing pressure). A reed instrument having N acoustical modes can be described as a 2N dimensional autonomous nonlinear dy-namical system. A reed-like instrument having two quasi-harmonic resonances, represented by a 4 dimensional dynamical system, is studied using the continuation and bifurcation software AUTO. Bifurcation diagrams are explored with respect to the blowing pressure, with focus on amplitude and frequency evolutions along the different solution branches. Some of the results are interpreted in terms of the ease of playing of the reed instrument. They can be interpreted as a theoretical illustration of the Bouasse-Benade prescription