1,274 research outputs found
Evolution of a model quantum system under time periodic forcing: conditions for complete ionization
We analyze the time evolution of a one-dimensional quantum system with an
attractive delta function potential whose strength is subjected to a time
periodic (zero mean) parametric variation . We show that for generic
, which includes the sum of any finite number of harmonics, the
system, started in a bound state will get fully ionized as . This
is irrespective of the magnitude or frequency (resonant or not) of .
There are however exceptional, very non-generic , that do not lead to
full ionization, which include rather simple explicit periodic functions. For
these the system evolves to a nontrivial localized stationary state
which is related to eigenfunctions of the Floquet operator
Singular normal form for the Painlev\'e equation P1
We show that there exists a rational change of coordinates of Painlev\'e's P1
equation and of the elliptic equation after which these
two equations become analytically equivalent in a region in the complex phase
space where and are unbounded. The region of equivalence comprises all
singularities of solutions of P1 (i.e. outside the region of equivalence,
solutions are analytic). The Painlev\'e property of P1 (that the only movable
singularities are poles) follows as a corollary. Conversely, we argue that the
Painlev\'e property is crucial in reducing P1, in a singular regime, to an
equation integrable by quadratures
Decay of a Bound State under a Time-Periodic Perturbation: a Toy Case
We study the time evolution of a three dimensional quantum particle,
initially in a bound state, under the action of a time-periodic zero range
interaction with ``strength'' (\alpha(t)). Under very weak generic conditions
on the Fourier coefficients of (\alpha(t)), we prove complete ionization as (t
\to \infty). We prove also that, under the same conditions, all the states of
the system are scattering states.Comment: LaTeX2e, 15 page
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