Lyman- α constraints on ultralight scalar dark matter: Implications for the early and late universe

Abstract

We investigate constraints on scalar dark matter (DM) by analyzing the Lyman-α forest, which probes structure formation at medium and small scales, and also by studying its cosmological consequences at high and low redshift. For scalar DM that constitutes more than 30% of the total DM density, we obtain a lower limit m 10 −21 eV for the mass of scalar DM. This implies an upper limit on the initial field displacement (or the decay constant for an axion-like field) of φ 10 16 GeV. We also derive limits on the energy scale of cosmic inflation and establish an upper bound on the tensor-to-scalar ratio of r < 10 −3 in the presence of scalar DM. Furthermore, we show that there is very little room for ultralight scalar DM to solve the "small-scale crisis" of cold DM without spoiling the Lyman-α forest results. The constraints presented in this paper can be used for testing generic theories that contain light scalar fields.

Looking for ultralight dark matter near supermassive black holes

“…Several other constraints on ULDM have appeared in the literature. The matter power spectrum revealed by Ly-α forest analyses is in tension with m 10 −21 eV [57][58][59][60][61] (see also [62,63]). Rotation curves of low-surface-brightness galaxies (LSBs) also disfavour m 10 −21 eV [35,44], if one accepts the soliton cores predicted by numerical simulations [22,23,64].…”

Constraints on anharmonic corrections of fuzzy dark matter

“…Aside from the standard searches for axions, there is a wealth of dedicated searches and projected experiments on the lookout for ultralight axions. These include studies of the neutral hydrogen distribution in the universe [31,32], laboratory constraints based on nuclear interactions [33], variation of fundamental constants [34,35], astrophysical bounds [36][37][38], gravitational wave searches [39,40] and analysis of CMB spectral distortions [41,42]. A prominent feature of the model is the presence of anharmonic corrections over the mass -2 -…”

Baryon-driven growth of solitonic cores in fuzzy dark matter halos

“…Consequently, stellar kinematic data of dark matter dominated dwarf spheroidal and ultra-diffuse galaxies favour a specific value for the scalar field mass, which is typically around m ∼ 10 −22 eV [8,[12][13][14][15][16][17]. This value is in conflict with Lyman-α forest observations constraining the field mass to roughly m > 10 −21 eV [18][19][20][21]. Less stringent constraints can be inferred from the high-z galaxy luminosity function [22][23][24][25][26].…”