**Dynamical
methods for linear Hamiltonian systems with applications to control process**,**
**

with Russell Johnson and Rafael Obaya,

The nonautonomous version of
the Yakubovich Frequency Theorem characterizes

the
solvability of an infinite horizon optimization problem in terms of the
validity of the

Frequency and Nonoscillation Conditions for a
linear Hamiltonian system, which is defined

from
the coefficients of the quadratic functional to be minimized. This paper
describes those

nonautonomous linear Hamiltonian systems satisfying the required properties. Two
groups

appear,
depending on whether they are uniformly weakly disconjugate
or not. It also contains

a
previous analysis of the long-term behavior of the Grassmannian
and Lagrangian flows

under
the presence of exponential dichotomy, which is required for the classification
and has

interest by
itself.