Decaying Dark Matter Phenomena in Cosmology

Decaying dark matter models posit that a fraction of the cold dark matter component is unstable on cosmological timescales, transforming into lighter particles that may be relativistic or semi-relativistic. Such decays inject energy and momentum into the cosmic fluid, leading to distinctive signatures in the expansion history, the growth of structure and the spectrum of density fluctuations. In two-body decay scenarios, the parent particle yields one massive and one massless or light daughter, the former receiving a characteristic velocity kick that suppresses clustering on small scales and can alleviate the so-called S8 tension between weak lensing and cosmic microwave background inferences.

These phenomena are of global significance since they offer a unified framework to address multiple observational tensions—from the amplitude of matter clustering to discrepancies in the Hubble constant and the primordial lithium abundance—without invoking entirely new exotic sectors. By altering the matter power spectrum at late times, decaying dark matter also impacts galaxy formation, the Lyman-α forest and the ionisation history of the intergalactic medium, thus providing a variety of observational avenues to constrain or detect such decays.

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Decaying Dark Matter Phenomena in Cosmology publication trend

The graph below shows the total number of articles in decaying dark matter phenomena in cosmology across all publications each year (not limited to Nature Index journals).

Technical terms

Decaying Dark Matter: Dark matter that transforms into lighter particles over cosmological timescales, altering energy and momentum distribution.

Matter Power Spectrum: Statistical representation of density fluctuations across spatial scales in the Universe.

Lyman-α Forest: Series of spectral absorption lines in quasar light due to intervening hydrogen clouds, tracing small-scale structure.

S8 Tension: Discrepancy in measurements of the amplitude of matter clustering derived from weak lensing surveys and cosmic microwave background observations.

Mass Splitting: Difference in mass between the parent dark matter particle and its decay products, influencing the velocity distribution of daughters.

References

1. Probing the two-body decaying dark matter scenario with weak lensing and the cosmic microwave background. Astronomy & Astrophysics (2024).
2. Decaying Dark Matter and Lyman-α forest constraints. Journal of Cosmology and Astroparticle Physics (2023).
3. Decaying dark matter, the H0 tension, and the lithium problem. Physical Review D (2021).