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Jean Nourrigat

Publications and source records attributed to Jean Nourrigat.

25 records · Page 2Linked to original sources

Weyl composition of symbols in large dimension

This paper is concerned with the Weyl composition of symbols in large dimension. We specify a class of symbols in order to estimate the Weyl symbol of the product of two Weyl $h-$pseudodifferential operators, with constants independent of the dimension. The proof includes a regularized and a hybrid compositions together with a decomposition formula. We also analyze in this context the remainder term of the semiclassical expansion of the Weyl composition.

math.AP↗

Bounded Weyl pseudodifferential operators in Fock space

We aim at constructing an analog of the Weyl calculus in an infinite dimensional setting, in which the usual configuration and phase spaces are ultimately replaced by infinite dimensional measure spaces, the so-called abstract Wiener spaces. The Hilbert space on which the operators act can be seen as a Fock space or, equivalently, as a space of square integrable functions on the configuration space. The construction is not straightforward and needs to split the configuration space into two factors, of which the first one is finite dimensional. Then one defines, for a convenient symbol $F$, a hybrid calculus, acting on the finite dimensional factor as a Weyl operator and on the other one as an anti-Wick operator, defined thanks to an infinite dimensional Segal-Bargmann transformation. One can establish bounds on the hybrid operators. These bounds enable us to prove the convergence of any sequence of hybrid operators associated with an increasing sequence of finite dimensional factors. Their common limit is the Weyl operator $OP_h^{weyl}(F)$, the analog of Calderón-Vaillancourt Theorem being a consequence of the upper mentionned bounds as well.

math.FA↗

Decay of Quantum Correlations in a Lattice by Heat Kernel Methods

We prove some estimations of the correlation of two local observables in quantum spin systems (with Schrödinger equations) at large temperature. For that, we describe the heat kernel of the Hamiltonian for a finite subset of the lattice, allowing the dimension to tend to infinity. This is an improved version of an earlier unpublished manuscript.

math-ph↗

Spectral Theory and Representations of Nilpotent Groups

We give an estimate of the number $N(λ)$ of eigenvalues $<λ$ for the image under an irreducible representation of the ``sublaplacian'' on a stratified nilpotent Lie algebra. We also give an estimate for the trace of the heat-kernel associated with this operator. The estimates are formulated in term of geometrical objects related to the representation under consideration. An important particular case is the Schrödinger equation with polynomial electrical and magnetical fields.

math.SP↗