A Does the unforced quartic oscillator behave chaotically?

[L_landau]

I thought that quartic oscillator is chaotic, but here
http://www.scholarpedia.org/article/Duffing_oscillator
it seems this is only when there is driving force.

It also says that for unforced quartic oscillator we can find equilibria and then determine if equilibria are stable or unstable. Is unstable equilibria chaotic?

Thanks

 

[wrobel]

There are a lot of different mathematical definitions of chaos. Which of them do you use?
Nevertheless, an autonomous Hamiltonian system with one degree of freedom is not chaotic in any reasonable sense

 

[L_landau]

In Hamiltonian formalism there would be two degrees of freedom I thought?

 

[wrobel]

In Hamiltonian formalism a system with Hamiltonian $H=H(q_1,\ldots,q_m,p_1,\ldots,p_m)$ by definition has $m$ degrees of freedom