and the rotation number for linear, non-autonomous Hamiltonian systems
with Roberta Fabbri and Russell Johnson,
Mat. Pura App. 185 (2006), S3-S21.
The rotation number for
non-autonomous Hamiltonian systems is used to characterize the
weak disconjugacy property for such systems. The argument functions of
are an important tool in the proofs. It is shown that weakly
disconjugate systems admit