Application, à un cristal de béryl,d'une nouvelle méthode d'étude par réflexion

The vibrational frequencies of beryl are determined from a measurement of the optical constants with a method utilizing reflexion from samples with and without an evaporated layer of an optically known substance.     

Poincaré, Einstein,et l’inertie de l’énergie

The mystery surrounding the discovery of the inertia of energy is solved by considering its connection with an older problem: the effect of uniform, global motion on the forces acting in an electric System. From Maxwell's and his disciples’ point of view this effect confirmed the existence of the ether. From Poincaré’ s point of view, it was paradoxical for it contradicted the relativity principle and went with a violation of the principle of reaction. The inertia of energy, as Einstein proposed it in 1905, answered these paradoxes in the framework of special relativity and in Poincaré’s style of reasoning.     

Cosmologies primordiales: Leurs variété, leurs constraintes

This paper presents some ingredients of the ≪new cosmology≫ that arose from the recent developments of high energy physics: non standard matter, extra dimensions and corrections to the Einstein-Hilbert lagrangian. Their cosmological effects will be illustrated by some examples. We shall insist on the theoretical constraints implied by the requirement that they should yield cosmological models without manifest pathologies and tending to the standard scenario.     

Random Unitary Matrices, Permutations and Painlevé

This paper is concerned with certain connections between the ensemble of n×n unitary matrices – specifically the characteristic function of the random variable tr(U) – and combinatorics – specifically Ulam's problem concerning the distribution of the length of the longest increasing subsequence in permutation groups – and the appearance of Painlevé functions in the answers to apparently unrelated questions. Among the results is a representation in terms of a Painlevé V function for the characteristic function of tr(U) and (using recent results of Baik, Deift and Johansson) an expression in terms of a Painlevé II function for the limiting distribution of the length of the longest increasing subsequence in the hyperoctahedral groups. Received: 2 December 1998 / Accepted: 12 May 1999     

Unification of Poincaré, BRST and Parisi-Sourlas supersymmetries

Poincaré, BRST and Parisi-Sourlas supersymmetries are usually viewed as unrelated. Here we argue that they are in fact closely related. We argue that fermions in Poincaré SUSY theories can be interpreted as negative-dimensional phase space coordinates, in the Parisi-Sourlas sense. The Bose-Fermi balance then implies that the effective phase space dimensionality vanishes. We show that interacting Poincaré SUSY theories are related to the corresponding free theories by superrotations similar to BRST transformations. For superstrings we find that spacetime can be viewed as a zero-dimensional manifold in the sense of Parisi-Sourlas.     

Evolution avec la température de la réflectivité, de l'indice complexe et de la sélectivité spectrale du nitrure de zirconium

The reflectance of zirconium nitride has been measured at 20, 500 and 700°C, within the range 0.22 to 5.50 μ m. The optical constants have been determined using Kramers-Kronig analysis. The spectral selectivity of this compound noticeably depends on temperature; the absorptance increases from 0.28 at 20°C to 0.36 at 700°C while the emittance increases from 0.06 to 0.14.     

Superconductivity,Pair Density Wave,and Néel Order in Cuprates

We investigate in underdoped cuprates possible coexistence of the superconducting order at zero momentum and pair density wave(PDW) at momentum Q=(π,π) in the presence of a Neel order.By symmetry,the d-wave uniform singlet pairing dS₀ can coexist with the d-wave triplet PDW dT_Q,and the p-wave singlet PDW pS_Q can coexist with the p-wave uniform triplet pT₀.At half filling,we find that the novel pS_Q+pT₀ state is energeticall.y more ...     

Influence des différents scénarios techniques, énergétiques et économiques sur la décision d'installer un nouvel échangeur de chaleur

Influence of different technical, energetic and economic scenarios on the decision of installing a new heat exchanger. This article proposes to examine the decision of installing a new heat exchanger in a working industrial unit in order to improve its energy performances. This examination is based on a new graphical method permitting us to approach the decision while taking into consideration the operating, technological and conjunctural variables.The analysis of the results shows that improvement in energy performances of an industrial unit does not always contribute to improving its economic performances. Factors that govern this contribution are in increasing importance: the choice of heat exchanger's configuration, the energy scenarios, the energy to be saved and the choice of the construction material of the heat exchanger.     

Handbook of Compressible Aerodynamics,by Jean Délery

Present knowledge of the constitution, structure and dynamics of the atmospheres of Venus and Jupiter are reviewed in the light of observations and measurements from recent space missions.     

Power, Lévy, exponential and Gaussian-like regimes in autocatalytic financial systems

We study by theoretical analysis and by direct numerical simulation the dynamics of a wide class of asynchronous stochastic systems composed of many autocatalytic degrees of freedom. We describe the generic emergence of truncated power laws in the size distribution of their individual elements. The exponents α of these power laws are time independent and depend only on the way the elements with very small values are treated. These truncated power laws determine the collective time evolution of the system. In particular the global stochastic fluctuations of the system differ from the normal Gaussian noise according to the time and size scales at which these fluctuations are considered. We describe the ranges in which these fluctuations are parameterized respectively by: the Lévy regime α < 2, the power law decay with large exponent ( α > 2), and the exponential decay. Finally we relate these results to the large exponent power laws found in the actual behavior of the stock markets and to the exponential cut-off detected in certain recent measurement. Received 29 July 2000 and Received in final form 25 September 2000     

La filière thorium,une option intéressante pour le nucléaire du futur

To satisfy a significant part of the primary energy demand at the world level by 2050, fission nuclear energy production has to grow by a large factor (more than 10). Due to the natural limitations of Uranium reserves (at a reasonable price) such a development makes necessary the use of breeder reactors. A comparative study of such breeder reactors using Uranium or Thorium based fuels shows that the use of Thorium based fuel has clear advantages in terms of flexibility, of minor actinides contents in the fuel cycle as well as for the inventory and disposal radiotoxicities. To cite this article: J.-M. Loiseaux et al., C. R. Physique 3 (2002) 1023–1034.