Achetions

Achetions are a hypothetical class of ultralight bosons posited in speculative physics and in some science-fiction works as a constituent of dark matter. They are envisioned as electrically neutral, non-baryonic particles with masses well below an electronvolt and extremely weak couplings to standard-model fields. In proposed models, achetions arise from a spontaneously broken achetonic U(1) symmetry, yielding a classical oscillating field that pervades space.

As a cosmic background, achetions are proposed to form a cold, collisionless component that can behave coherently on galactic scales. Depending on their de Broglie wavelength and self-interactions, they may imprint wave-like features on structure formation, potentially suppressing small-scale fluctuations relative to traditional cold dark matter. Some models also include a hypothetical long-range achetonic force or a faint coupling to photons, which could enable indirect effects in astrophysical environments or precision experiments.

Experimental status is speculative and unsettled. Researchers discuss potential detection strategies in cosmology, precision spectroscopy, and laboratory detectors aimed at ultralight particles, as well as astrophysical observations of stellar cooling and magnetically influenced phenomena. However, there is no confirmed empirical evidence for achetions, and their existence remains a topic of debate within theoretical and speculative communities.

In fiction and exploratory theory, achetions offer a flexible framework for addressing dark matter puzzles and for exploring physics beyond the Standard Model without committing to a single, established mechanism.