Special Session 23: Evolution Equations and Integrable Systems

Linear Evolution Equations Revisited via the Fokas Unified Transform Method
Andreas Chatziafratis
National and Kapodistrian University of Athens
Greece
Co-Author(s):    
Abstract:
We survey some of our recent research results relating to construction of explicit solutions (closed-form integral representations), in the classical sense, as well as to qualitative theory for non-homogeneous initial-boundary-value and interface problems for a variety of linear (systems of) evolution partial differential equations (PDE) with constant and with variable coefficients. Such PDE emerge in connection to a plethora of natural phenomena and mathematical models in physics, biology, chemical engineering, finance and other applied sciences; examples include continuum mechanics, heat transfer, biomedicine, electron optics, and battery technology. Our research program relies on, explores and extends the applicability of the celebrated complex-analytic unified transform method of Fokas. This is joint work with a large global network of collaborators. Notable findings include: long-range instabilities (see e.g. [A. Chatziafratis, T. Ozawa, S.-F. Tian, “Rigorous analysis of the unified transform method and long-range instabilities for the inhomogeneous time-dependent Schrödinger equation on the quarter-plane”, Math. Annalen, 2023] and [A. Chatziafratis, L. Grafakos, S. Kamvissis, Long-range instabilities for linear evolution PDE on semi-bounded domains via the Fokas method, Dyn. PDE, 2024]), time-asymptotic break-down effects (e.g. [J.L. Bona, A. Chatziafratis, H. Chen, S. Kamvissis, “The linear BBM-equation on the half-line revisited”, Lett. Math. Phys., 2024]), and counter-examples to solution uniqueness (e.g. [A. Chatziafratis, A. Miranville, G. Karali, A.S. Fokas, E.C. Aifantis, "Higher-order diffusion and Cahn-Hilliard-type models revisited on the half-line", Math. Models Methods Appl. Sci., 2025] and [A. Chatziafratis, S. Kamvissis, “Infinity of solutions to initial-boundary value problems for linear constant-coefficient evolution PDEs on semi-infinite intervals”, Bull. London Math. Soc., 2025])