Hiroshima Mathematical Analysis Seminar
Forthcoming Seminars
Date : January 9, 2026 (Friday)
Time : 16:30 -- 17:30
Place : A201, School of Science
Speaker : Doctor Takuya Sato (University of Tokyo)
Title : TBA
Date : December 5, 2025 (Friday)
Time : 15:00 -- 16:00
Place : A201, School of Science; if you are interested in this seminar, click here and register.
Speaker : Doctor Nobutatsu Kobayashi (Tokyo University of Science)
Title : Global well-posedness for a Zakharov type system in bounded domains
Time : 16:30 -- 17:30
Place : A201, School of Science; if you are interested in this seminar, click here and register.
Speaker : Doctor Taiki Okazaki (Tohoku University)
Date : November 28, 2025 (Friday)
Time : 16:30 -- 17:30
Place : A201, School of Science; if you are interested in this seminar, click here and register.
Speaker : Professor Naoto Yamaoka (Osaka Metropolitan University)
Title : Separatrices in generalized Liénard systems and an application to a cliodynamic model
Abstract : In this talk, we study the separatrices of generalized Liénard systems, which are classical models for analyzing nonlinear oscillations. By using phase plane analysis, we show that certain families of negative trajectories do not cross a given curve, thereby clarifying the qualitative behavior of solutions near the separatrix. As an application, we consider a model in cliodynamics proposed by Peter Turchin, where the dependent variables represent the territorial extent of an empire and its social cohesion. By making a suitable change of variables, this model is transformed into a generalized Liénard-type system, and under certain conditions, we show the existence of an unstable limit cycle that explains the oscillatory rise and fall observed in the dynamics of historical empires. This talk is based on joint work with Jitsuro Sugie (Shimane University).
Japanese Version
Go to the analysis group home page
Go to the math department home page