Determination of the composition of rarefied neutral atmospheres by mass spectrometers carried on high-speed spacecraft

The quantitative measurement of atomic and molecular O2 in rarefied atmospheres by mass spectrometers onboard high speed spacecraft is reported. Data are also given on instrument performance in high speed molecular beams and in the fly through mode

An explicit model for the adiabatic evolution of quantum observables driven by 1D shape resonances

This paper is concerned with a linearized version of the transport problem where the Schr\"{o}dinger-Poisson operator is replaced by a non-autonomous Hamiltonian, slowly varying in time. We consider an explicitly solvable model where a semiclassical island is described by a flat potential barrier, while a time dependent 'delta' interaction is used as a model for a single quantum well. Introducing, in addition to the complex deformation, a further modification formed by artificial interface conditions, we give a reduced equation for the adiabatic evolution of the sheet density of charges accumulating around the interaction point.Comment: latex; 26 page

Payment systems, inside money and financial intermediation

This paper assesses the impact of introducing an efficient payment system on the amount of credit provided by the banking system. Two channels are investigated. First, innovations in wholesale payments technology enhance the security and speed of deposits as a payment medium for customers and therefore affect the split between holdings of cash and the holdings of deposits that can be intermediated by the banking system. Second, innovations in wholesale payments technology help establish well-functioning interbank markets for end-of-day funds, which reduces the need for banks to hold excess reserves. The authors examine these links empirically using payment system reforms in Eastern European countries as a laboratory. The analysis finds evidence that reforms led to a shift away from cash in favor of demand deposits and that this in turn enabled a prolonged credit expansion in the sample countries. By contrast, while payment system innovations also led to a reduction in excess reserves in some countries, this effect was not causal for the credit boom observed in these countries.Banks&Banking Reform,Debt Markets,Bankruptcy and Resolution of Financial Distress,Access to Finance,Currencies and Exchange Rates

Adiabatic evolution of 1D shape resonances: an artificial interface conditions approach

Artificial interface conditions parametrized by a complex number $\theta_{0}$ are introduced for 1D-Schr\"odinger operators. When this complex parameter equals the parameter $\theta\in i\R$ of the complex deformation which unveils the shape resonances, the Hamiltonian becomes dissipative. This makes possible an adiabatic theory for the time evolution of resonant states for arbitrarily large time scales. The effect of the artificial interface conditions on the important stationary quantities involved in quantum transport models is also checked to be as small as wanted, in the polynomial scale $(h^N)_{N\in \N}$ as $h\to 0$, according to $\theta_{0}$.Comment: 60 pages, 13 figure

Spectral asymptotics for large skew-symmetric perturbations of the harmonic oscillator

Originally motivated by a stability problem in Fluid Mechanics, we study the spectral and pseudospectral properties of the differential operator $H_\epsilon = -\partial_x^2 + x^2 + i\epsilon^{-1}f(x)$ on $L^2(R)$, where $f$ is a real-valued function and $\epsilon > 0$ a small parameter. We define $\Sigma(\epsilon)$ as the infimum of the real part of the spectrum of $H_\epsilon$, and $\Psi(\epsilon)^{-1}$ as the supremum of the norm of the resolvent of $H_\epsilon$ along the imaginary axis. Under appropriate conditions on $f$, we show that both quantities $\Sigma(\epsilon)$, $\Psi(\epsilon)$ go to infinity as $\epsilon \to 0$, and we give precise estimates of the growth rate of $\Psi(\epsilon)$. We also provide an example where $\Sigma(\epsilon)$ is much larger than $\Psi(\epsilon)$ if $\epsilon$ is small. Our main results are established using variational "hypocoercive" methods, localization techniques and semiclassical subelliptic estimates.Comment: 38 pages, 4 figure

Optimal non-reversible linear drift for the convergence to equilibrium of a diffusion

We consider non-reversible perturbations of reversible diffusions that do not alter the invariant distribution and we ask whether there exists an optimal perturbation such that the rate of convergence to equilibrium is maximized. We solve this problem for the case of linear drift by proving the existence of such optimal perturbations and by providing an easily implementable algorithm for constructing them. We discuss in particular the role of the prefactor in the exponential convergence estimate. Our rigorous results are illustrated by numerical experiments

Accurate WKB Approximation for a 1D Problem with Low Regularity

2000 Mathematics Subject Classification: 34L40, 65L10, 65Z05, 81Q20.This article is concerned with the analysis of the WKB expansion in a classically forbidden region for a one dimensional boundary value Schrodinger equation with a non smooth potential. The assumed regularity of the potential is the one coming from a non linear problem and seems to be the critical one for which a good exponential decay estimate can be proved for the first remainder term. The treatment of the boundary conditions brings also some interesting subtleties which require a careful application of Carleman’s method

Equity finance, adverse selection and product market competition

This paper analyses the effect of asymmetric information between a firm and its outside investors on the firm's competitive position in a model where first-period competition is followed by a financing stage a la Myers and Majluf (1984). In our model, interim profit generated by the competition stage takes the role of financial slack and determines the extent to which external equity finance is required for a new investment opportunity. I consider the full set of equilibria in our version of the Myers and Majluf model and formally analyse financial slack as a comparative statics variable. Using this, I derive the firm's first period objective from first principles. In contrast to models of predatory behavior, I find that in the presence of an adverse selection problem the need to finance externally may provide a strategic benefit rather than a strategic disadvantage. The reason is that the adverse selection problem may induce speculative behavior, which will make the firm more aggressive vis a vis its rival

Bose Einstein condensate in the Lowest Landau Level : Hamiltonian dynamics

Ce texte est une prépublication de l'IRMAR.Dans un article antérieur avec A. Aftalion et X. Blanc, les propriétés d'hypercontractivité du semigroupe des dilatations dans des espaces de fonctions entières est apparu comme un outil essentiel de l'étude du modèle de plus bas niveau de Landau pour les condensats de Bose Einstein. Ce travail portait sur le problème stationnaire. Nous abordons ici la question de la dynamique Hamiltonienne et les problèmes de stabilité spectrale. A MODIFIED VERSION OF THIS PREPRINT HAS BEEN PUBLISHED IN REVIEWS IN MATHEMATICAL PHYSICS