The Hubble constant troubled by dark matter in non-standard cosmologies

Abstract

The Standard Cosmological Model has experienced tremendous success at reproducing observational data by assuming a universe dominated by a cosmological constant and dark matter in a flat geometry. However, several studies, based on local measurements, indicate that the universe is expanding too fast, in disagreement with the Cosmic Microwave Background. Taking into account combined data from CMB, Baryon Acoustic Oscillation, and type Ia Supernovae, we show that if the mechanism behind the production of dark matter particles has at least a small non-thermal origin, one can induce larger values of the Hubble rate $$H_0$$ H 0 , within the $$\Lambda$$ Λ CDM, to alleviate the trouble with $$H_0$$ H 0 . In the presence of non-standard cosmology, however, we can fully reconcile CMB and local measurements and reach $$H_0=70$$ H 0 = 70 –74 $${\text {km s}}^{-1}\,{\text {Mpc}}^{-1}$$ km s - 1 Mpc - 1 .

The H 0 trouble: confronting non-thermal dark matter and phantom cosmology with the CMB, BAO, and Type Ia supernovae data

“…On the other hand, previous analyses of the cases with τ ≥ 10 5 have been already done in ref. [15]. There, it was shown that the mechanism used here works well for dark matter mother lifetime below 10 5 s, as you can see in figure 3 in that reference.…”

“…Interestingly, there is a positive correlation between ∆N eff and the Hubble parameter (H 0 ) [7]. In other words, the formula mentioned above could potentially increase H 0 [14][15][16]32]. However, in our work, we will assess whether this extra source of radiation can indeed raise H 0 and alleviate the Hubble tension without altering much other well-known cosmological parameters.…”

“…This range for the lifetime was chosen to avoid conflicts with the Big Bang Nucleosynthesis data. Longer lifetimes are excluded because the injection of relativistic particles at late times alters the abundance of the light elements [15]. These values for the mass ratio and lifetime are the prior values used in the CMB analyses in section 3.…”

“…In this way, early-time measurement of the Hubble constant is influenced by it, leading to a higher value of H 0 , in the direction of values extracted from late-time observations [9,12]. In particular, we consider a non-thermal production mechanism of dark matter particles that produces a boost factor larger than one, thus increasing the relativistic energy density in the early universe, which in turn has the potential to raise H 0 and ultimately alleviate the tension [13][14][15][16]. In other words, this setup increases the number of relativistic degrees of freedom, i.e.…”

The hubble rate trouble: an effective field theory of dark matter

“…Given the existing upper limit on the chemical potential, we can limit the energy injection at a given time. The bounds are rather stringent, but for τ > 10 4 s. In our work, we will focus on the region of parameter space in which τ < 10 4 s, to avoid conflicts with BBN [29,52].…”