Biomedical subjects

Benoît Grémaud

Publications and source records attributed to Benoît Grémaud.

4 recordsLinked to original sources

PubMed2005

Semiclassical analysis of real atomic spectra beyond Gutzwiller's approximation.

Real atomic systems, like the hydrogen atom in a magnetic field or the helium atom, whose classical dynamics are chaotic, generally present both discrete and continuous symmetries. In this paper, we explain how these properties must be taken into account in order to obtain the proper (i.e., symmetry projected) h expansion of semiclassical expressions like the Gutzwiller trace formula. In the case of the hydrogen atom in a magnetic field, we shed light on the excellent agreement between present theory and exact quantum results.

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PubMed2004

Bloch oscillations of ultracold atoms: a tool for a metrological determination of h/m Rb.

We use Bloch oscillations in a horizontal moving standing wave to transfer a large number of photon recoils to atoms with a high efficiency (99.5% per cycle). By measuring the photon recoil of 87Rb, using velocity-selective Raman transitions to select a subrecoil velocity class and to measure the final accelerated velocity class, we have determined h/m(Rb) with a relative precision of 0.4 ppm. To exploit the high momentum transfer efficiency of our method, we are developing a vertical standing wave setup. This will allow us to measure h/m(Rb) better than 10(-8) and hence the fine structure constant alpha with an uncertainty close to the most accurate value coming from the (g-2) determination.

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PubMed2002

Quantum modes on chaotic motion: Analytically exact results.

We discover a class of chaotic quantum systems for which we obtain some analytically exact eigenfunctions in closed form. These results have been possible due to connections shown between random matrix models, many-body theories, and dynamical systems. We believe that these results and connections will pave the way to a better understanding of quantum chaos.

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PubMed2002

Planck's over 2 pi corrections in semiclassical formulas for smooth chaotic dynamics.

The validity of semiclassical expansions in the power of Planck's over 2 pi for the quantum Green's function have been extensively tested for billiards systems, but in the case of chaotic dynamics with smooth potential, even if formulas are existing, a quantitative comparison is still missing. In this paper, extending the theory developed by Gaspard et al. [Adv. Chem. Phys. 90, 105 (1995)], based on the classical Green's functions, we present an efficient method allowing the calculation of Planck's over 2 pi corrections for the propagator, the quantum Green's function, and their traces. In particular, we show that the previously published expressions for Planck's over 2 pi corrections to the traces are incomplete.

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