Unfolding the geometric structure and multiple timescales of the urea-urease pH oscillator
under review
- We study a two-variable dynamical system modeling pH oscillations in the urea–urease reaction within giant lipid vesicles – a problem that intrinsically contains multiple, well-separated timescales. Building on an existing, deterministic formulation via ordinary differential equations, we resolve different orders of magnitude within a small parameter and analyze the system's limit cycle behavior using geometric singular perturbation theory (GSPT). By introducing two different coordinate scalings – each valid in a distinct region of the phase space – we resolve the local dynamics near critical fold points, using the extension of GSPT through such singular points due to Krupa and Szmolyan. This framework enables a geometric decomposition of the periodic orbits into slow and fast segments and yields closed-form estimates for the period of oscillation. In particular, we link the existence of such oscillations to an underlying biochemical asymmetry, namely, the differential transport across the vesicle membrane.
| Author: | Arthur StraubeORCiD, Guillermo Olicón Méndez, Stefanie Winkelmann, Felix Höfling, Maximilian Engel |
|---|---|
| Document Type: | Article |
| Year of first publication: | 2025 |
| ArXiv Id: | http://arxiv.org/abs/2508.07275 |

