Disconjugacy
and the rotation number for linear, non-autonomous Hamiltonian systems
with Roberta Fabbri and Russell Johnson,
Ann.
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
Lidskii-Yakubovich
are an important tool in the proofs. It is shown that weakly
disconjugate systems admit
principal solutions.
