http://arxiv.org/abs/2110.04322
We consider a non-minimally coupled scalar field as a potential cold dark matter candidate. These models are natural extensions of the ultra-light axion (ULA) models which are based on minimally coupled scalar fields. For a non-minimally coupled field, the scalar field energy density behaves as radiation at early times, which yields a bound on the coupling constant, $\xi \lesssim 10$, from the primordial nucleosynthesis theory. The first-order perturbations of the non-minimally coupled field with adiabatic initial conditions cause the gravitational potential to decay on large scales. A comparison of the cosmological data with the theoretical matter power spectrum yields the following constraint on the coupling constant: $\xi \lesssim 0.01$. We also consider isocurvature modes in our analysis. We argue that a mix of adiabatic and isocurvature initial conditions for a non-minimally coupled scalar field might allow one to obtain the usual adiabatic CDM power spectrum.
K. Sankharva and S. Sethi
Tue, 12 Oct 21
35/73
Comments: 14 pages, 7 figures
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