Cosmological implications of ultralight axionlike fields

By V. Poulin, Tristan L. Smith, D. Grin, Tanvi Karwal, M. Kamionkowski. Physical Review D, 2018

202 citations recorded by the source corpus.

Cosmological observations are used to test for imprints of an ultralight axionlike field (ULA), with a range of potentials $V(\ensuremath{\phi})\ensuremath{\propto}[1\ensuremath{-}\mathrm{cos}(\ensuremath{\phi}/f){]}^{n}$ set by the axion-field value $\ensuremath{\phi}$ and decay constant $f$. Scalar field dynamics dictate that the field is initially frozen and then begins to oscillate around its minimum when the Hubble parameter drops below some critical value. For $n=1$, once dynamical, the axion energy density dilutes as matter; for $n=2$ it dilutes as radiation and for $n=3$ it dilutes faster than radiation. Both the homogeneous evolution of the ULA and the dynamics of its linear perturbations are included, using an effective fluid approximation generalized from the usual $n=1$ case. ULA models are parametrized by the redshift ${z}_{c}$ when the field becomes dynamical, the fractional energy density ${f}_{{z}_{c}}\ensuremath{\equiv}{\mathrm{\ensuremath{\Omega}}}_{a}({z}_{c})/{\mathrm{\ensuremath{\Omega}}}_{\mathrm{tot}}({z}_{c})$ in the axion field at ${z}_{c}$, and the effective sound speed ${c}_{s}^{2}$. Using Planck, BAO and JLA data, constraints on ${f}_{{z}_{c}}$ are obtained. ULAs are degenerate with dark energy for all three potentials if $1+{z}_{c}\ensuremath{\lesssim}10$. When $3\ifmmode\times\else\texttimes\fi{}{10}^{4}\ensuremath{\gtrsim}1+{z}_{c}\ensuremath{\gtrsim}10$, ${f}_{{z}_{c}}$ is constrained to be $\ensuremath{\lesssim}0.004$ for $n=1$ and ${f}_{{z}_{c}}\ensuremath{\lesssim}0.02$ for the other two potentials. The constraints then relax with increasing ${z}_{c}$. These results have implications for ULAs as a resolution to cosmological tensions, such as discrepant measurements of the Hubble constant, or the EDGES measurement of the global 21 cm signal.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/7a0d81e850c75e181988206695e6009f6497af8b

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Nuclear and High Energy Physics

Citations in the corpus

The Hubble Tension and Early Dark Energy (2022, background): “Another possibility (15, 96) is a scalar field with a smooth “slowroll” potential like those considered for inflation or quintessence.”
Cosmology Intertwined II: The Hubble Constant Tension (2020, unknown): “[150] V.”
Cosmology with a very light Lμ − Lτ gauge boson (2019, background): “Scenarios involving early dark energy [16–18] or a component of decaying dark matter [19] have also been proposed to address this tension.”
Recent Progress in the Physics of Axions and Axion-Like Particles (2020, background): “There are a number of constraints on this mass range from CMB [69–71], pulsar timing array (PTA) [72], Lyman-α forest [73, 74], and ultra-faint dwarf galaxy (Eridanus II) [75], which are depicted in Fig.”
The Simons Observatory: science goals and forecasts (2018, background): “…oscillates, and the ULAs transition from behaving more like scalar field dark energy to being a darkmatter-like cosmological component, which has strong cosmological implications for structure formation (Schive et al. 2016; Armengaud et al. 2017; Poulin et al. 2018; Fairbairn et al. 2018).”
Resolving the Hubble tension with new early dark energy (2020, methodology): “[32] V.”
Constraining early dark energy with large-scale structure (2020, unknown): “, [35–37]).”