The long delayed solution of the Bukhvostov Lipatov model

In this paper I complete the solution of the Bukhvostov Lipatov model by computing the physical excitations and their factorized S matrix. I also explain the paradoxes which led in recent years to the suspicion that the model may not be integrable.Comment: 9 page

Pourquoi calculer un indicateur du climat des affaires dans les services ?

L’enquête mensuelle de conjoncture de la Banque de France présente chaque mois un indicateur du climat des affaires dans l’industrie. Un indicateur similaire a été construit pour les services, en appliquant une méthode analogue, à savoir l’extraction d’un facteur d’évolution qui est commun à l’ensemble des questions de l’enquête mensuelle dans les services.Analyse conjoncturelle, données d’enquête, services, interpolation, composantes principales.

L’indicateur synthétique mensuel d’activité (ISMA) : une révision.

L’ISMA est un des principaux outils de diagnostic conjoncturel de la Banque de France. Publié chaque mois, il estime la croissance du PIB français pour le prochain trimestre, en se basant sur les données d’enquêtes de la Banque de France.Analyse conjoncturelle, prévision du PIB, étalonnages, données d’enquête.

Single particle Green's function in the Calogero-Sutherland model for rational couplings β=p/q\beta=p/q

We derive an exact expression for the single particle Green function in the Calogero-Sutherland model for all rational values of the coupling $\beta$. The calculation is based on Jack polynomial techniques and the results are given in the thermodynamical limit. Two type of intermediate states contribute. The firts one consists of a particle propagating out of the Fermi sea and the second one consists of a particle propagating in one direction, q particles in the opposite direction and p holes.Comment: 9 pages, RevTeX, epsf.tex, 4 figures, files uuencode

Correlation functions of disorder operators in massive ghost theories

The two-dimensional ghost systems with negative integral central charge received much attention in the last years for their role in a number of applications and in connection with logarithmic conformal field theory. We consider the free massive bosonic and fermionic ghost systems and concentrate on the non-trivial sectors containing the disorder operators. A unified analysis of the correlation functions of such operators can be performed for ghosts and ordinary complex bosons and fermions. It turns out that these correlators depend only on the statistics although the scaling dimensions of the disorder operators change when going from the ordinary to the ghost case. As known from the study of the ordinary case, the bosonic and fermionic correlation functions are the inverse of each other and are exactly expressible through the solution of a non-linear differential equation.Comment: 8 pages, late

Dynamical correlation functions in the Calogero-Sutherland model

We compute the dynamical Green function and density-density correlation in the Calogero-Sutherland model for all integer values of the coupling constant. An interpretation of the intermediate states in terms of quasi-particles is found.Comment: 20pgs, (1 reference added

Form-factors computation of Friedel oscillations in Luttinger liquids

We show how to analytically determine for $g\leq 1/2$ the "Friedel oscillations" of charge density by a single impurity in a 1D Luttinger liquid of spinless electrons.Comment: Revtex, epsf, 4pgs, 2fig

Hyperelliptic curves for multi-channel quantum wires and the multi-channel Kondo problem

We study the current in a multi-channel quantum wire and the magnetization in the multi-channel Kondo problem. We show that at zero temperature they can be written simply in terms of contour integrals over a (two-dimensional) hyperelliptic curve. This allows one to easily demonstrate the existence of weak-coupling to strong-coupling dualities. In the Kondo problem, the curve is the same for under- and over-screened cases; the only change is in the contour.Comment: 7 pages, 1 figure, revte

Boundary interactions changing operators and dynamical correlations in quantum impurity problems

Recent developments have made possible the computation of equilibrium dynamical correlators in quantum impurity problems. In many situations however, one is rather interested in correlators subject to a non equilibrium initial preparation; this is the case for instance for the occupation probability $P(t)$ in the double well problem of dissipative quantum mechanics (DQM). We show in this paper how to handle this situation in the framework of integrable quantum field theories by introducing ``boundary interactions changing operators''. We determine the properties of these operators by using an axiomatic approach similar in spirit to what is done for form-factors. This allows us to obtain new exact results for $P(t)$; for instance, we find that that at large times (or small $g$), the leading behaviour for g < 1/2} is $P(t)\propto e^{-\Gamma t}\cos\Omega t$, with the universal ratio. $\Omega/\Gamma = \cot {\pi g}/{2(1-g)}$.Comment: 4 pages, revte

Empirical likelihood estimation of the spatial quantile regression

The spatial quantile regression model is a useful and flexible model for analysis of empirical problems with spatial dimension. This paper introduces an alternative estimator for this model. The properties of the proposed estimator are discussed in a comparative perspective with regard to the other available estimators. Simulation evidence on the small sample properties of the proposed estimator is provided. The proposed estimator is feasible and preferable when the model contains multiple spatial weighting matrices. Furthermore, a version of the proposed estimator based on the exponentially tilted empirical likelihood could be beneficial if model misspecification is suspect