P. Exner, T. Ichinose, H. Neidhardt, and V.A. Zagrebnov
New product formulae and quantum Zeno dynamics with generalized 
observables
(46K, LaTeX)

ABSTRACT.  We demonstrate a pair of new product formulae which combine a
projection with a resolvent of a positive operator, or with an
exponential function and spectral projections, respectively. The
convergence is strong or even operator-norm under more restrictive
assumptions. The second mentioned formula can be used to describe
Zeno dynamics in the situation when the usual non-decay
measurement is replaced by a particular generalized observable in
the sense of Davies.