Using the homological link theorem and iteration inequalities of Maslov-type index, we prove the multiplicity of subharmonic solutions for some variant subquadratic non-autonomous Hamiltonian systems. Moreover, the minimal period problem has also been considered for the variant subquadratic autonomous Hamiltonian systems.
"Subharmonic solutions and minimal periodic solutions of first-order variant subquadratic Hamiltonian systems." Topol. Methods Nonlinear Anal. 55 (2) 517 - 532, 2020. https://doi.org/10.12775/TMNA.2019.105