Search results for "scattering [lepton nucleus]"
showing 10 items of 508 documents
Determining a Random Schrödinger Operator : Both Potential and Source are Random
2020
We study an inverse scattering problem associated with a Schr\"odinger system where both the potential and source terms are random and unknown. The well-posedness of the forward scattering problem is first established in a proper sense. We then derive two unique recovery results in determining the rough strengths of the random source and the random potential, by using the corresponding far-field data. The first recovery result shows that a single realization of the passive scattering measurements uniquely recovers the rough strength of the random source. The second one shows that, by a single realization of the backscattering data, the rough strength of the random potential can be recovered…
Spectral approach to the scattering map for the semi-classical defocusing Davey–Stewartson II equation
2019
International audience; The inverse scattering approach for the defocusing Davey–Stewartson II equation is given by a system of D-bar equations. We present a numerical approach to semi-classical D-bar problems for real analytic rapidly decreasing potentials. We treat the D-bar problem as a complex linear second order integral equation which is solved with discrete Fourier transforms complemented by a regularization of the singular parts by explicit analytic computation. The resulting algebraic equation is solved either by fixed point iterations or GMRES. Several examples for small values of the semi-classical parameter in the system are discussed.
Explicit Characterization of Inclusions in Electrical Impedance Tomography
2001
In electrical impedance tomography one seeks to recover the spatial conductivity distribution inside a body from knowledge of the Neumann--Dirichlet map. In many practically relevant situations the conductivity is smooth apart from some inhomogeneities where the conductivity jumps to a higher or lower value. An explicit characterization of these inclusions is developed in this paper. To this end a class of dipole-like indicator functions is introduced, for which one has to check whether their boundary values are contained in the range of an operator determined by the measured Neumann--Dirichlet map. It is shown that this holds true if and only if the dipole singularity lies inside the inhom…
Direct method for calculating temperature-dependent transport properties
2015
We show how temperature-induced disorder can be combined in a direct way with first-principles scattering theory to study diffusive transport in real materials. Excellent (good) agreement with experiment is found for the resistivity of Cu, Pd, Pt (and Fe) when lattice (and spin) disorder are calculated from first principles. For Fe, the agreement with experiment is limited by how well the magnetization (of itinerant ferromagnets) can be calculated as a function of temperature. By introducing a simple Debye-like model of spin disorder parameterized to reproduce the experimental magnetization, the temperature dependence of the average resistivity, the anisotropic magnetoresistance and the spi…
Inelastic neutron scattering due to acoustic vibrations confined in nanoparticles: theory and experiment
2008
The inelastic scattering of neutrons by nanoparticles due to acoustic vibrational modes (energy below 10 meV) confined in nanoparticles is calculated using the Zemach-Glauber formalism. Such vibrational modes are commonly observed by light scattering techniques (Brillouin or low-frequency Raman scattering). We also report high resolution inelastic neutron scattering measurements for anatase TiO2 nanoparticles in a loose powder. Factors enabling the observation of such vibrations are discussed. These include a narrow nanoparticle size distribution which minimizes inhomogeneous broadening of the spectrum and the presence of hydrogen atoms oscillating with the nanoparticle surfaces which enhan…
Singularity formation in the Gross-Pitaevskii equation and collapse in Bose-Einstein condensates
2004
We study the mechanisms of collapse of the condensate wave function in the Gross-Pitaevskii theory with attractive interparticle interaction. We reformulate the Gross-Pitaevskii equation as Newton's equations for a flux of particles, and introduce the collapsing fraction of particles. We assume that this collapsing fraction is expelled from the condensate due to dissipation. Using this hypothesis we analyze the dependence of the collapse behavior on the initial conditions. We find that, for a properly chosen negative scattering length, the remnant fraction of atoms becomes larger when the initial aspect ratio of the condensate is increased.
Search for a heavy Higgs boson decaying into a Z boson and another heavy Higgs boson in the ℓℓbb final state in pp collisions at s=13 TeV with the AT…
2018
A search for a heavy neutral Higgs boson, A, decaying into a Z boson and another heavy Higgs boson, H, is performed using a data sample corresponding to an integrated luminosity of 36.1 fb(-1) from ...
Entanglement interferometry for precision measurement of atomic scattering properties.
2003
We report on a two-particle matter wave interferometer realized with pairs of trapped 87Rb atoms. Each pair of atoms is confined at a single site of an optical lattice potential. The interferometer is realized by first creating a coherent spin-mixture of the two atoms and then tuning the inter-state scattering length via a Feshbach resonance. The selective change of the inter-state scattering length leads to an entanglement dynamics of the two-particle state that can be detected in a Ramsey interference experiment. This entanglement dynamics is employed for a precision measurement of atomic interaction parameters. Furthermore, the interferometer allows to separate lattice sites with one or …
Investigation of Feshbach resonances in ultracold K40 spin mixtures
2017
Magnetically tunable Feshbach resonances are an indispensable tool for experiments with atomic quantum gases. We report on 37 thus far unpublished Feshbach resonances and four further probable Feshbach resonances in spin mixtures of ultracold fermionic $^{40}\mathrm{K}$ with temperatures well below 100 nK. In particular, we locate a broad resonance at $B=389.7\phantom{\rule{0.16em}{0ex}}\text{G}$ with a magnetic width of $26.7\phantom{\rule{0.28em}{0ex}}\text{G}$. Here $1\phantom{\rule{0.28em}{0ex}}\text{G}={10}^{\ensuremath{-}4}\phantom{\rule{0.16em}{0ex}}\text{T}$. Furthermore, by exciting low-energy spin waves, we demonstrate a means to precisely determine the zero crossing of the scatte…
Polyoxometalates: From Magnetic Models to Multifunctional Materials
2002
In this article we have presented some recent achievements of the polyoxometalates in the fields of molecular magnetism and functional molecular materials. In the context of the molecular magnetism we have shown that POMs provide ideal examples of magnetic clusters with coexisting ferro and antiferromagnetic exchange interactions which can be investigated using a variety of magnetic techniques, including the Inelastic Neutron Scattering spectroscopy, to get a thorough characterization of the magnetic levels in these large clusters, and to test the validity of the spin hamiltonians commonly used in magnetism.