Explicit complex time integrators for stiff problems
Numerical Analysis
2026-01-13 v1 Numerical Analysis
Mathematical Physics
Complex Variables
math.MP
Quantum Physics
Abstract
Most numerical methods for time integration use real-valued time steps. Complex time steps, however, can provide an additional degree of freedom, as we can select the magnitude of the time step in both the real and imaginary directions. We show that specific paths in the complex time plane lead to expanded stability regions, providing clear computational advantages for complex-valued systems. In particular, we highlight the Schr\"odinger equation, for which complex time integrators can be uniquely optimal. Furthermore, we demonstrate that these benefits extend to certain classes of real-valued stiff systems by coupling complex time steps with the Projective Integration method.
Cite
@article{arxiv.2601.07730,
title = {Explicit complex time integrators for stiff problems},
author = {Jithin D. George and Julian Koellermeier and Samuel Y. Jung and Niall M. Mangan},
journal= {arXiv preprint arXiv:2601.07730},
year = {2026}
}