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ISSN 2562-2854 (print)

ISSN 2562-2862 (online)

# New Proofs of Monotonicity of Period Function for Cubic Elliptic Hamiltonian

In [1] S.-N. Chow and J. A. Sanders proved that the period function is monotone for elliptic Hamiltonian of degree 3. In this paper we significantly simplify their proof, and give a new way to prove this fact, which may be used in other problems.