10 research outputs found
On eigenfunction approximations for typical non-self-adjoint Schroedinger operators
We construct efficient approximations for the eigenfunctions of
non-self-adjoint Schroedinger operators in one dimension. The same ideas also
apply to the study of resonances of self-adjoint Schroedinger operators which
have dilation analytic potentials. In spite of the fact that such
eigenfunctions can have surprisingly complicated structures with multiple local
maxima, we show that a suitable adaptation of the JWKB method is able to
provide accurate lobal approximations to them.Comment: 17 pages, 11 figure
On the Born-Oppenheimer approximation of diatomic molecular resonances
We give a new reduction of a general diatomic molecular Hamiltonian, without
modifying it near the collision set of nuclei. The resulting effective
Hamiltonian is the sum of a smooth semiclassical pseudodifferential operator
(the semiclassical parameter being the inverse of the square-root of the
nuclear mass), and a semibounded operator localised in the elliptic region
corresponding to the nuclear collision set. We also study its behaviour on
exponential weights, and give several applications where molecular resonances
appear and can be well located.Comment: 22 page
Wigner's Dynamical Transition State Theory in Phase Space: Classical and Quantum
A quantum version of transition state theory based on a quantum normal form
(QNF) expansion about a saddle-centre-...-centre equilibrium point is
presented. A general algorithm is provided which allows one to explictly
compute QNF to any desired order. This leads to an efficient procedure to
compute quantum reaction rates and the associated Gamov-Siegert resonances. In
the classical limit the QNF reduces to the classical normal form which leads to
the recently developed phase space realisation of Wigner's transition state
theory. It is shown that the phase space structures that govern the classical
reaction d ynamicsform a skeleton for the quantum scattering and resonance
wavefunctions which can also be computed from the QNF. Several examples are
worked out explicitly to illustrate the efficiency of the procedure presented.Comment: 132 pages, 31 figures, corrected version, Nonlinearity, 21 (2008)
R1-R11
Semiclassical complex interactions at a non-analytic turning point
We continue a dominant WKB solution of
the Schr\"odinger equation in the classically forbidden region to an
outgoing WKB solution in the classically allowed region across a simple (multi-dimensional) turning point, without assuming the analyticity for the potential.
This report explains briefly the method used in \cite{bfm}, where we computed the semiclassical asymptotics of the width of shape resonances
for non-globally analytic potentials
Width of shape resonances for non globally analytic potentials
We consider the semiclassical Schroedinger operator with a well-in-an-island potential, on which we assume C-infinity smoothness only, except near infinity. We give the asymptotic expansion of the imaginary part of the shape resonance at the bottom of the well. This is a generalization of a result by Helffer and Sj"ostrand in the globally analytic case.
We use an almost analytic extension in order to continue the WKB solution coming from the well beyond the caustic set, and, for the justification of the accuracy of this approximation, we develop some refined microlocal arguments in h-dependent small regions
Semiclassical complex interactions at a non-analytic turning point
We continue a dominant WKB solution of the Schr\"odinger equation in the classically forbidden region to an outgoing WKB solution in the classically allowed region across a simple (multi-dimensional) turning point, without assuming the analyticity for the potential. This report explains briefly the method used in \cite{bfm}, where we computed the semiclassical asymptotics of the width of shape resonances for non-globally analytic potentials