Energy–mass relation of emitted quanta in the memory-burden phase

Ascertain the functional relationship between black-hole mass and the typical energy of emitted quanta after the semi-classical description breaks down and the memory-burden phase begins, specifically whether the effective emission temperature remains fixed (no-burst scenario) or continues to increase with decreasing mass (burst scenario).

Background

Predictions for the dark-matter momentum distribution depend sensitively on how the emission temperature behaves during the memory-burden phase. The authors study two prescriptions: a constant-temperature ‘no burst’ model and a time-evolving ‘burst’ model where temperature increases as mass decreases, analogous to the semi-classical regime.

The lack of a definitive description of the energy–mass relation in the memory-burden regime introduces substantial uncertainty into the high-energy tail and overall shape of the dark-matter velocity distribution, with direct consequences for Lyman-α forest constraints.

References

However, at this point, there is no clear indication how the relation between the BH mass and the energy of the emitted quanta evolves when the SC description breaks down, see e.g.~the discussion in Ref.. In this paper, we consider two prescriptions for the evaporation rate during the MB phase.

Non-Cold Dark Matter from Memory-Burdened Primordial Black Holes  (2604.00090 - Thoss et al., 31 Mar 2026) in Section 2.3, Semi-Classical Evaporation Followed by a Memory-Burden Stage