Semicontinuity
of the derivative of the rotation number
with Rafael Obaya,
C. R.
Math. Acad. Sci. Paris, Serie I 320
(1995), 1245-1248.
This note is concerned with the
study of the one-dimensional Schrödinger
equation. Let A2
be the set of those energies for which the projective flow
admits an invariant measure with square integrable density function. We
prove the continuous variation of an adequate family of linear measures
and deduce that the derivative of the rotation number is lower
semicontinuous on A2.
