3 papers
math.SG2025
Action-angle coordinates of spherical pendulums with symmetric quadratic potentials
Chengle Peng, Xiudi Tang
We study the spherical pendulum system with an arbitrary potential function , which is an integrable system with a first integral whose Hamiltonian flow is periodic. We…
math.SG2024
A note on the symplectic classification of almost-toric systems
Xiudi Tang
Since simple semitoric systems were classified about fifteen years ago, and semitoric systems five years ago, we want to move a step forward to almost-toric systems. We give a clas…
math.SG2024
Symplectic excision
Yael Karshon, Xiudi Tang
We use time-independent incomplete Hamiltonian flows to excise interesting closed subsets of positive codimension from symplectic manifolds. Examples of such subsets include what w…