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On the Mean Field and Classical Limits of Quantum Mechanics
No full text38 pages. A few typos have been corrected in this new version, to appear in Communications in Mathematical Physics.International audienceThe main result in this paper is a new inequality bearing on solutions of the -body linear Schrödinger equation and of the mean field Hartree equations. This inequality implies that the mean field limit of the quantum mechanics of identical particles is uniform in the classical limit and provides a quantitative estimate of the quality of the approximation. This result applies to the case of interaction potentials. The quantity measuring the approximation of the -body quantum dynamics by its mean field limit is analogous to the Monge-Kantorovich (or Wasserstein) distance with exponent . The inequality satisfied by this quantity is reminiscent of the work of Dobrushin on the mean field limit in classical mechanics [Func. Anal. Appl. 13 (1979), 115-123]. Our approach of this problem is based on a direct analysis of the -particle Liouville equation, and avoids using techniques based on the BBGKY hierarchy or on second quantization
Ion transport through deformable porous media: derivation of the macroscopic equations using upscaling
No full textInternational audienceWe study the upscaling or homogenization of the transport of a multicomponentelectrolyte in a dilute Newtonian solvent through a deformable porous medium.The pore scale interaction between the flow and the structure deformation is taken into account.After a careful adimensionalization process, we first consider so-called equilibrium solutions,in the absence of external forces, for which the velocity and diffusive fluxes vanish andthe electrostatic potential is the solution of a Poisson-Boltzmann equation.When the motion is governed by a small static electric field and small hydrodynamic and elastic forces,we use O'Brien's argument to deduce a linearized model. Then we perform the homogenizationof these linearized equations for a suitable choice of time scale. It turns out thatthe deformation of the porous medium is weakly coupled to the electrokinetics systemin the sense that it does not influence electrokinetics although the latter one yieldsan osmotic pressure term in the mechanical equations. As a byproduct we find that theeffective tensor satisfies Onsager properties, namely is symmetric positive definite
Search for vector-like charge 2/3 T quarks in proton-proton collisions at sqrt(s) = 8 TeV
No full textsee paper for full list of authorsInternational audienceA search for fermionic top quark partners T of charge 2/3 is presented. The search is carried out in proton-proton collisions corresponding to an integrated luminosity of 19.7 inverse femtobarns collected at a center-of-mass energy of sqrt(s) = 8 TeV with the CMS detector at the LHC. The T quarks are assumed to be produced strongly in pairs and can decay into tH, tZ, and bW. The search is performed in five exclusive channels: a single-lepton channel, a multilepton channel, two all-hadronic channels optimized either for the bW or the tH decay, and one channel in which the Higgs boson decays into two photons. The results are found to be compatible with the standard model expectations in all the investigated final states. A statistical combination of these results is performed and lower limits on the T quark mass are set. Depending on the branching fractions, lower mass limits between 720 and 920 GeV at 95% confidence level are found. These are among the strongest limits on vector-like T quarks obtained to date
Origin of energetic ions observed in the terrestrial ion foreshock : 2D full-particle simulations
No full textInternational audienceCollisionless shocks are well-known structures in astrophysical environments which dissipate bulk flow kinetic energy and accelerate large fraction of particle. Spacecrafts have firmly established the existence of the so-called terrestrial foreshock region magnetically connected to the shock and filled by two distinct populations in the quasi- perpendicular shock region (i.e. for 45 ̊ ≤ ΘBn ≤ 90 ̊, where ΘBn is the angle between the shock normal and the upstream magnetic field) : (i) the field-aligned ion beams or “ FAB ” characterized by a gyrotropic distribution, and (ii) the gyro-phase bunched ions or “ GPB ” characterized by a NON gyrotropic distribution. The present work is based on the use of two dimensional PIC simulation of a curved shock and associated foreshock region where full curvature effects, time of flight effects and both electrons and ions dynamics are fully described by a self consistent approach.Our previous analysis (Savoini et Lembège, 2015) has evidenced that these two types of backstreaming populations can originate from the shock front itself without invoking any local diffusion by ion beam instabilities. Present re- sults are focussed on individual ion trajectories and evidence that "FAB" population is injected into the foreshock mainly along the shock front whereas the "GPB" population penetrates more deeply the shock front. Such differ- ences explain why the "FAB" population loses their gyro-phase coherency and become gyrotropic which is not the case for the "GPB". The impact of these different injection features on the energy gain for each ion population will be presented in détails
Observed correlation of Venus topography with the zonal wind and albedo at cloud top level: the role of stationary gravity waves.
No full textInternational audienceBased on the analysis of UV images (at 365 nm) of Venus cloud top (altitude 67±2 km) collected with VMC (Venus Monitoring Camera) on board Venus Express (VEX), it is found that the zonal wind speed south of the equator (from 5◦S to 15◦s) shows a conspicuous variation (from -101 to -83 m/s) with geographic longitude of Venus, correlated with the underlying relief of Aphrodite Terra. We interpret this pattern as the result of stationary gravity waves produced at ground level by the up lift of air when the horizontal wind encounters a mountain slope. These waves can propagate up to cloud top level, break there and transfer their momentum to the zonal flow. Such upward propagation of gravity waves and influence on the wind speed vertical profile was shown to play an important role in the middle atmosphere of the Earth by Lindzen [1981], but is not reproduced in a current GCM of Venus atmosphere.Consistent with present findings, the two VEGA mission balloons experienced a small, but significant, difference of westward velocity, at their 53 km floating altitude.The albedo at 365 nm varies also with longitude and latitude in a pattern strikingly similar in the low latitude regions to a recent map of cloud top H2O [Fedorova et al., 2015], in which a lower UV albedo is correlated with increased H2O. We argue that H2O enhancement is the sign of upwelling, suggesting that the UV absorber is also brought to cloud top by upwelling
Taming reluctant random walks in the positive quadrant
No full textInternational audienceA lattice walk model is said to be reluctant if the defining step set has a strong drift towards the boundaries. We describe efficient random generation strategies for these walks
Density and temperature characterization of long-scale length, near-critical density controlled plasma produced from ultra-low density plastic foam
No full textInternational audienceThe ability to produce long-scale length (i.e. millimeter scale-length), homogeneous plasmas is of interest in studying a wide range of fundamental plasma processes. We present here a validated experimental platform to create and diagnose uniform plasmas with a density close or above the critical density. The target consists of a polyimide tube filled with an ultra low-density plastic foam where it was heated by x-rays, produced by a long pulse laser irradiating a copper foil placed at one end of the tube. The density and temperature of the ionized foam was retrieved by using x-ray radiography and proton radiography was used to verify the uniformity of the plasma. Plasma temperatures of 5–10 eV and densities around 10 21 cm −3 are measured. This well-characterized platform of uniform density and temperature plasma is of interest for experiments using large-scale laser platforms conducting High Energy Density Physics investigations
A global Riemann-Hilbert problem for two-dimensional inverse scattering at fixed energy
No full textInternational audienceWe develop the Riemann-Hilbert problem approach to inverse scattering for the two-dimensional Schrodinger equation at fixed energy. We obtain global or generic versions of the key results of this approach for the case of positive energy and compactly supported potentials. In particular, we do not assume that the potential is small or that Faddeev scattering solutions do not have singularities (i.e. we allow the Faddeev exceptional points to exist). Applications of these results to the Novikov-Veselov equation are also considered
Measurement of the CP-violating weak phase phi[s] and the decay width difference DeltaGamma[s] using the Bs to J/Psi phi(1020) decay channel in pp collisions at sqrt(s) = 8 TeV
No full textSubmitted to Phys. Lett. B ; see paper for full list of authorsInternational audienceThe CP-violating weak phase phi[s] of the Bs meson and the decay width difference DeltaGamma[s] of the Bs light and heavy mass eigenstates are measured with the CMS detector at the LHC using a data sample of Bs to J/Psi phi(1020) to mu+mu-K+K- decays. The analysed data set corresponds to an integrated luminosity of 19.7 inverse femtobarns collected in pp collisions at a centre-of-mass energy of 8 TeV. A total of 49200 reconstructed Bs decays are used to extract the values of phi[s] and DeltaGamma[s] by performing a time-dependent and flavour-tagged angular analysis of the mu+mu-K+K- final state. The weak phase is measured to be phi[s] = -0.075 +/- 0.097 (stat) +/- 0.031 (sys) rad, and the decay width difference is DeltaGamma[s] = 0.095 +/- 0.013 (stat) +/- 0.007 (sys) inverse picoseconds
Explicit formulas and global uniqueness for phaseless inverse scattering in multidimensions
No full textInternational audienceWe consider phaseless inverse scattering for the Schrödinger equation with compactly supported potential in dimension d ≥ 2. We give explicit formulas for solving this problem from appropriate data at high energies. As a corollary, we give also a global uniqueness result for this problem with appropriate data on a fixed energy neighborhood