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math.DS2025
High-order persistence of resonant caustics in perturbed circular billiards
Comlan Edmond Koudjinan, Rafael RamÃrez-Ros
We find necessary and sufficient conditions for high-order persistence of resonant caustics in perturbed circular billiards. The main tool is a perturbation theory based on the Bia…
math.DS2024
Birkhoff Conjecture for nearly centrally symmetric domains
Vadim Kaloshin, Comlan Edmond Koudjinan, Ke Zhang
In this paper we prove a perturbative version of a remarkable Bialy-Mironov (Ann.Math:389-413(196), 2022) result. They prove non perturbative Birkhoff conjecture for centrally-symm…