Strategic activities in support of young French SMEs

In this paper we closely study young French Small and Medium Enteprises (SMEs). We highlight the structure of this target firms and we build a typology of corresponding business models. The business models stemming from this typology are typical (to the greatest extent possible) and actionable. We are particularly intersted in indentifying groups of SMEs where gouvernement assistance would be particularly effective and strategically valuable for the national economy. One of our conclusins is that the typology is not based on a classical growth model that reflects progressive phases of developement in the life of a young firm. Furthermore, it is ineffective and wasteful to focus governement assistance efforts on firms based on their age. We identify groups of business models where assistance would be more effecient and strategically more effective.SME ; growth ; growth model ; typology

Study of impurities in spin-Peierls systems including lattice relaxation

The effects of magnetic and non-magnetic impurities in spin-Peierls systems are investigated allowing for lattice relaxation and quantum fluctuations. We show that, in isolated chains, strong bonds form next to impurities, leading to the appearance of magneto-elastic solitons. Generically, these solitonic excitations do not bind to impurities. However, interchain elastic coupling produces an attractive potential at the impurity site which can lead to the formation of bound states. In addition, we predict that small enough chain segments do not carry magnetic moments at the ends

A New Method for the Determination of the Real Part of the Hadron Elastic Scattering Amplitude at Small Angles and High Energies

A new method for the determination of the real part of the elastic scattering amplitude is examined for high energy proton-proton elastic scattering at small momentum transfer. This method allows us to decrease the number of model assumptions, to obtain the real part in a narrow region of momentum transfer and to test different models. The real part is computed at a given point t_min near t=0 from the known Coulomb amplitude. Hence one obtains an important constraint on the real part of the forward scattering amplitude and therefore on the rho-parameter (measuring the ratio of the real to imaginary part of the scattering amplitude at t=0), which can be tested at LHC.Comment: 10 pages and 5 figures. Final published form in Physics Letters

From spinons to magnons in explicit and spontaneously dimerized antiferromagnetic chains

We reconsider the excitation spectra of a dimerized and frustrated antiferromagnetic Heisenberg chain. This model is taken as the simpler example of compiting spontaneous and explicit dimerization relevant for Spin-Peierls compounds. The bosonized theory is a two frequency Sine-Gordon field theory. We analize the excitation spectrum by semiclassical methods. The elementary triplet excitation corresponds to an extended magnon whose radius diverge for vanishing dimerization. The internal oscilations of the magnon give rise to a series of excited state until another magnon is emited and a two magnon continuum is reached. We discuss, for weak dimerization, in which way the magnon forms as a result of a spinon-spinon interaction potential.Comment: 5 pages, latex, 3 figures embedded in the tex

Simulations of pure and doped low-dimensional spin-1/2 gapped systems

Low dimensional spin-1/2 systems with antiferromagnetic interactions display very innovative features, driven by strong quantum fluctuations. In particular, geometrical effects or competing magnetic interactions can give rise to the formation of a spin gap between the singlet ground state and the first excited triplet state. In this chapter, we focus on the numerical investigation of such systems by Exact Diagonalisation methods and some extensions of it including a simultaneous mean-field treatment of some perturbative couplings. After a presentation of the Lanczos algorithm and a description of the space group symmetries, we give a short review on some pure low-dimensionnal frustrated spin gapped systems. In particular, we outline the role of the magnetic frustration in the formation of disordered phase. A large part is also devoted to frustrated Spin-Peierls systems for which the role of interchain couplings as well as impurity doping effects has been studied numerically.Comment: Chapter book in Quantum Magnetism, Lecture Notes in Physics (2004

Phase diagram of a Heisenberg spin-Peierls model with quantum phonons

Using a new version of the density-matrix renormalization group we determine the phase diagram of a model of an antiferromagnetic Heisenberg spin chain where the spins interact with quantum phonons. A quantum phase transition from a gapless spin-fluid state to a gapped dimerized phase occurs at a non-zero value of the spin-phonon coupling. The transition is in the same universality class as that of a frustrated spin chain, which the model maps to in the anti-adiabatic limit. We argue that realistic modeling of known spin-Peierls materials should include the effects of quantum phonons.Comment: RevTeX, 5 pages, 3 eps figures included using epsf. Improved theories in adiabatic and non-adiabatic regimes give better agreement with DMRG. This version accepted in Physical Review Letter

Hydrodynamic identification of NAUTILUS FOWT platform from small scale tests

A small-scale tank test campaign of the NAUTILUS offshore wind floating semisub-mersible platform was held at the Ifremer Deep Water Basin within the framework of the MaRINET 2 project. The support structure consists in four stabilized columns on a square pontoon supporting a generic 8-MW wind turbine. The tests were carried out at 1:36 Froude scale in parked conditions, and the mooring system was modelled as a set of aerial mooring springs providing a nonlinear stiffness. The hydrodynamic characterization of the floater from experimental data was tackled by using traditional techniques in naval architecture), as well as approaches derived from operational modal analysis in the frequency domain, such as the Sub Space Identification—Covariance (SSI-COV) method. The validity of this approach and its potential application to the identification of such kind of structures is discussed against the results of a more traditional technique based on the fitting of decay tests

First Measurement of Proton-Proton Elastic Scattering at RHIC

The first result of the pp2pp experiment at RHIC on elastic scattering of polarized protons at sqrt{s} = 200 GeV is reported here. The exponential slope parameter b of the diffractive peak of the elastic cross section in the t range 0.010 <= |t| <= 0.019 (GeV/c)^2 was measured to be b = 16.3 +- 1.6 (stat.) +- 0.9 (syst.) (GeV/c)^{-2} .Comment: 9 pages 5 figure