Talk:Ostrogradsky instability
Add topicLatest comment: 7 months ago by ~2025-43277-60 in topic "Hamiltonian unbounded from below"
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"Jacobian" should be "Hessian matrix determinant"?
[edit]There is a mention of the Jacobian, but it refers to a matrix of mixed second derivatives, so I think Hessian is more appropriate. 31.154.68.30 (talk) 09:34, 1 January 2025 (UTC)
"Hamiltonian unbounded from below"
[edit]What is the significance of this? The source [1] says something about spurious "excitations", implying quantum mechanics. Am I to understand that a classical system wouldn't have the "instability" problem? Also I dont understand how this physically rules out 3rd order dynamical theories. Couldn't we just suppose a Dirac sea filling all negative energy states? ~2025-43277-60 (talk) 03:02, 28 December 2025 (UTC)