Generalize fitness-irrelevance theorems beyond smooth, bounded, time-independent settings

Extend the discrete and continuum fitness-irrelevance theorems for uniformly competitive phenotype-switching systems to rough coefficients, unbounded higher-dimensional phenotype spaces, and switching rates that vary in time, including treatment-dependent switching rates.

Background

The paper proves asymptotic irrelevance of fitness for finite compartmental systems and for continuum phenotype-structured equations under uniform competition. The stated results assume time-independent switching and smooth coefficients; the continuum result is one-dimensional on the main domain considered, with higher-dimensional extensions covered only for bounded phenotype spaces through companion work.

The authors explicitly identify rough coefficients, unbounded higher-dimensional phenotype spaces, and time-dependent switching as settings not covered by the present theorems. These extensions are important for modeling treatment-induced changes in phenotypic transition rates and realistic, potentially unbounded, multidimensional phenotype spaces.

References

Extending them to rough coefficients, to unbounded higher-dimensional phenotype spaces, and to switching rates that change in time (for instance under treatment) is open.

— Stochastic gradient descent on the epigenetic landscape: a unified framework for cellular plasticity, tumor heterogeneity, and the asymptotic irrelevance of fitness  (2609.37703 - Fassoni, 29 Sep 2026) in Section 'Conclusion and outlook', subsection 'Future directions'

In simulations with fast, well-connected switching we always observed convergence to u_{\rm eq}; whether this holds in general is open.

— Stochastic gradient descent on the epigenetic landscape: a unified framework for cellular plasticity, tumor heterogeneity, and the asymptotic irrelevance of fitness  (2609.37703 - Fassoni, 29 Sep 2026) in Appendix A, Remark 'Sustained oscillations under weighted competition'