Showing papers by "Université Paris-Saclay published in 1995"
Journal Article•
TL;DR: In this article, the authors studied the initial-value problems for the Davey-Stewartson systems and the Ishimori equations and proved the existence of global small solutions of these equations for the elliptic-hyperbolic and hyperbolic-Hyperbolic cases in some analytic function spaces.
Abstract: We study the initial-value problems for the Davey-Stewartson systems and the Ishimori equations. Elliptic-hyperbolic and hyperbolic-elliptic cases were treated by the inverse scattering techniques ([2--4, 10, 13--15, 32] for the Davey-Stewartson systems and [28, 29, 33] for the Ishimori equations). Elliptic-elliptic and hyperbolic-elliptic cases were studied (in [16, 17] for the Davey-Stewartson systems and [31] for the Ishimori equations) without the use of the inverse scattering techniques. Existence of a weak solution to the Davey-Stewartson systems for the elliptic-hyperbolic case is also obtained in [16] with a smallness condition on the data in $L^2$ and a blow-up result was also obtained for the elliptic-elliptic case. By using the sharp smoothing property of solutions to the linear Schrodinger equations the local existence of a unique solution to the Davey-Stewartson systems for the elliptic-hyperbolic and hyperbolic-hyperbolic cases was established in [30] in the usual Sobolev spaces with a smallness condition on the data. We prove the local existence of a unique solution to the Davey-Stewartson systems for the elliptic-hyperbolic and hyperbolic-hyperbolic cases in some analytic function spaces without a smallness condition on the data. Furthermore we prove existence of global small solutions of these equations for the elliptic-hyperbolic and hyperbolic-hyperbolic cases in some analytic function spaces.
41 citations
TL;DR: In this article, the limb to limb Lyman-alpha reflectivities observed with the Voyager ultraviolet spectrometer (UVS) instruments during the fly-by of Saturn are reanalyzed using a revised H Lyman alpha sensitivity for the Voyager 1 instrument.
27 citations
TL;DR: In this paper, the DELPHI detector was used to measure three-particle correlations in e+e− annihilations at LEP using data collected by the DelphI detector.
26 citations
TL;DR: In this paper, a measurement of the Δ++(1232) inclusive production in hadronic decays of the Z at LEP is presented, based on 1.3 million hadronic events collected by the DELPHI detector in the 1994 LEP running period.
15 citations
TL;DR: The high repulsive states of HgAr and HgNe van der Waals complexes, correlating with Hg 6s6d atomic states have been investigated by double resonance spectroscopy, through the first excited state A 30+ and B 31 of the complexes as mentioned in this paper.
Abstract: The high repulsive states of HgAr and HgNe van der Waals complexes, correlating with Hg 6s6d atomic states have been investigated by double resonance spectroscopy, through the first excited state A 30+ and B 31 of the complexes. The repulsive potentials have been fitted through numerical Franck–Condon simulations. They have been characterized by perturbative calculation as quasi‐pure 6dΣ potentials in Hund’s case a. The strong Hg–rare gas electrostatic interaction potential overruns the spin–orbit interaction at distances shorter than 7 A. These observed repulsive states are mostly of Ω=1 character correlating with 3D3 at infinite distances. The contribution from the potential of Ω=0− symmetry correlating with 1D2 is of minor importance. Therefore, the absorption in the repulsive states of the complex arises mostly from proximity induced absorption in an optically forbidden transition 3P1→3D3. A perturbative model accounts well for the bound free absorption intensities experimentally observed.
7 citations
TL;DR: The correlation exponent of the corresponding low-energy Hamiltonian shows that singlet (extended [ital s]-wave) superconductivity has the most rapidly diverging susceptibility as [ital T][r arrow]0 ([ital K][sub [rho]][gt]1), located close to a phase-separation instability of the model.
Abstract: The exact ground-state energy [ital E][sub 0]([Phi]) is calculated for a one-dimensional copper-oxide model defined on a ring of finite length [ital L], threaded by an external flux [Phi]. It includes on-site and nearest-neighbor intersite Coulomb repulsion [ital V], as well as a nonzero bare oxide'' gap [Delta][sub 0] between the orbitals in the unit cell. The correlation exponent [ital K][sub [rho]] of the corresponding low-energy Hamiltonian shows that singlet (extended [ital s]-wave) superconductivity has the most rapidly diverging susceptibility as [ital T][r arrow]0 ([ital K][sub [rho]][gt]1). This superconducting phase is located close to a phase-separation instability of the model, indicated by [ital K][sub [rho]][r arrow][infinity]. Longer range of the Coulomb interaction tends to frustrate phase separation, enhances the range of [ital V] for which [ital K][sub [rho]][gt]1, and slightly broadens the regime of [ital V] where 1[lt][ital K][sub [rho]][lt][infinity].
6 citations
TL;DR: In this paper, it was shown that anisotropy in the pairing interaction always enhances the superconducting temperature Tc, thanks to a general theorem in matrix theory, and that such an anisotropic interaction also gives rise to different partial-wave pairings than in the corresponding isotropic cases.
Abstract: We give a simple demonstration that anisotropy (of arbitrary strength) in the pairing interaction (of arbitrary origin) always enhances the superconducting temperature Tc, thanks to a general theorem in matrix theory. Moreover, such an anisotropic interaction also gives rise to different partial-wave pairings than in the corresponding isotropic cases. A particular example, treated rigorously in the weak-coupling regime, explicitly exhibits, depending on the anisotropy parameters, either singlet pairing (as an admixture of s (l = 0) and d (l = 2) waves), or triplet (l = 1) pairings. We discuss the possible implications of our results for actual physical systems as well as their plausible link with d-wave pairing often invoked for high-Tc materials.
5 citations
TL;DR: In this article, microscopic characterization of GaAs layers with small Fe-based precipitates was performed using transmission electron microscopy, with mean diameters ranging from 21 to 47 nm and number densities from 1013-1015 per cm3.
Abstract: GaAs layers that contain small Fe‐based precipitates have been grown using molecular‐beam epitaxy. The layers were produced either by codepositing Fe during GaAs growth or by first depositing a thin layer of an Fe‐Ga alloy and then growing a capping layer of GaAs. Microstructural characterization of the layers was performed by using transmission electron microscopy. For those samples in which the Fe alloy layer was deposited, the layer disappeared after GaAs growth, leaving behind Fe‐containing precipitates distributed throughout the GaAs overlayer. Precipitates were also formed in Fe codeposited samples. The sizes and number densities of the precipitates were dependent on the growth method used, with mean diameters ranging from 21 to 47 nm and number densities from 1013–1015 per cm3. The phase, orientation, and morphology of the particles were also dependent on the growth conditions used, with FeAs and Fe being observed.
4 citations
TL;DR: Theorem 4.7 as discussed by the authors shows that the pairing is perfect when r > 2 and K^/K is quasi-regular in the sense of [Ngl], i.e., when K can be embedded in an extension of K whose Galois group is a free prop-group.
Abstract: where X is the twist of X by a certain involution on A. Specifically, we show in Theorem 4.7 that the pairing is perfect when r > 2 and K^/K is quasi-regular in the sense of [Ngl], i.e., when K^/K can be embedded in an extension of K whose Galois group is a free prop-group. Global fields are a source of examples of quasi-regular extensions: if K^ l K is an extension of global fields with Galois group isomorphic to 2p9 and if there is only one prime of ̂ above/?, then the localizatiqn ofK^/Kat a prime abovepis quasi-regular (Prop. 4.2).
3 citations
TL;DR: In this article, the Fermi surface of the organic conductor (TMTSF) was studied through the measurements of magnetic quantum oscillations, and it was shown that the magnetic field-induced spin-density waves are strongly modified upon application of pressure, which may explain the absence of superconductivity.
TL;DR: In this paper, the evolution under sustained shear of an ordered crystal with B2 structure is studied by Monte-Carlo simulation: the effect of shearing is modelled by shifts of atomic planes, while thermally activated atomic diffusion is promoted by the motion of one vacancy.
Abstract: The evolution under sustained shear of an ordered crystal with B2 structure is studied by Monte-Carlo simulation: the effect of shearing is modelled by shifts of atomic planes, while thermally activated atomic diffusion is promoted by the motion of one vacancy. The tricritical point expected in the dynamical phase diagram from mean field theories and from Monte-Carlo simulations in the limit of weak driving (few atoms shifted at once) does not appear in such simulations, much in the same way as for “large cascade size” in alloys under irradiation. However an unexpected bifurcation in microstructures is observed which could be related to the order-disorder transition experimentally observed under ball-milling.