Axion cosmology in the presence of non-trivial Nambu-Goldstone modes

TL;DR

This paper reevaluates axion cosmology considering kinetic Nambu-Goldstone modes, revealing that their effects can hinder axion dark matter formation in some models but enable alternative cosmological phenomena in extended symmetry scenarios.

Contribution

It demonstrates how kinetic Nambu-Goldstone modes influence axion cosmology, introducing new features like ultralight dark matter, dark energy, and long-range forces in extended PQ symmetry models.

Findings

Kinetic Nambu-Goldstone modes can prevent axion dark matter in certain models.

Extended PQ symmetry models produce ultralight dark matter and dark energy.

New cosmological phenomena such as long-range spin-dependent forces and slow-roll inflation emerge.

Abstract

Axion cosmology is reexamined taking into account effect of kinetic pseudo Nambu-Goldstone modes, with its importance recently pointed out. When Peccei-Quinn (PQ) symmetry is broken by a chiral U(1) singlet, it is found that the effect of kinetic Nambu-Goldstone mode makes the axion dark matter untenable. When PQ symmetry is extended and is broken by two singlets, we find axion cosmology to work, but there are several differences from the axion cosmology studied in the literature. The differences are (1) ordinary type of dark matter scaling as $1/{\rm cosmic \; scale\; factor}^3$ arising from a modulus field and not from the usual angular field, (2) mass of the dark matter quantum in the ultralight range, $(10^{-32} \sim 10^{-14})\,$eV, (3) emergence of dark energy with the present density of order (a few meV)$^4$ consistent with observations, (4) presence of a long range spin-dependent force, (5) slow-roll inflation after PQ symmetry breaking when conformal coupling to gravity is introduced.