Determine which long-term effect controls orbital-period evolution

Determine whether mass transfer from the companion star to the white dwarf or angular-momentum-loss effects dominate the long-term orbital-period evolution of cataclysmic variables.

Background

The paper challenges the conventional view that cataclysmic variables universally evolve from longer to shorter orbital periods. It identifies several effects that can increase the period, including conservative mass transfer from the lower-mass companion to the white dwarf and mass ejection during nova eruptions, while angular-momentum loss tends to decrease the period.

Although the available period-change measurements show that many systems have increasing periods, the relative importance of mass transfer and angular-momentum loss remains unresolved. The question is central to determining whether cataclysmic variables generally evolve toward shorter periods, longer periods, or different directions depending on system properties.

References

I do not know whether the mass-transfer or AML effects will dominate.

— Classical Nova V1405 Cas Had $M_{\rm ejecta}$$>$$M_{\rm accreted}$ and so is Unlikely to be a Type Ia Supernova Progenitor  (2609.10990 - Schaefer, 10 Sep 2026) in Section 7.5, “CV evolution runs from long-P to short-P”

Although uncertainties remain about the form and strength of magnetic braking, growing evidence from recent observations and numerical modeling suggests that magnetic braking saturates in rapidly rotating low-mass main-sequence stars \citep{El-Badry_2022}.

— A Comprehensive Study of the Long-Period Cataclysmic Variable V630 Cassiopeiae  (2609.30669 - Zamora et al., 25 Sep 2026) in Section 1, Introduction, p. 30