993 research outputs found
Unified Superfluid Dark Sector
We present a novel theory of a unified dark sector, where late-time cosmic
acceleration emerges from the dark matter superfluid framework. The system is
described by a superfluid mixture consisting of two distinguishable states with
a small energy gap, such as the ground state and an excited state of dark
matter. Given their contact in the superfluid, interaction between those states
can happen, converting one state into the other. This long range interaction
within the superfluid couples the two superfluid phonon species through a
cosine potential motivated by Josephson/Rabi interactions. As a consequence of
this potential, a new dynamics of late-time accelerated expansion emerges in
this system, without the need of dark energy, coming from a universe containing
only this two-state DM superfluid. Because the superfluid species are
non-relativistic, their sound speeds remain suitably small throughout the
evolution. We calculate the expansion history and growth of linear
perturbations, and compare the results to CDM cosmology. For the
fiducial parameters studied here, the predicted expansion and growth function
are close to those of CDM, but the difference in the predicted growth
rate is significant at late times. The present theory nicely complements the
recent proposal of dark matter superfluidity to explain the empirical success
of MOdified Newtonian Dynamics (MOND) on galactic scales, thus offering a
unified framework for dark matter, dark energy, and MOND phenomenology.Comment: 27 pages, 4 figures. v2: Version accepted in JCA
Resolving the Hubble tension with Early Dark Energy
Early dark energy (EDE) offers a solution to the so-called Hubble tension.
Recently, it was shown that the constraints on EDE using Markov Chain Monte
Carlo are affected by prior volume effects. The goal of this paper is to
present constraints on the fraction of EDE, , and the Hubble
parameter, , which are not subject to prior volume effects. We conduct a
frequentist profile likelihood analysis considering Planck cosmic microwave
background, BOSS full-shape galaxy clustering, DES weak lensing, and SH0ES
supernova data. Contrary to previous findings, we find that for the EDE
model is in statistical agreement with the SH0ES direct measurement at for all data sets. For our baseline data set (Planck + BOSS), we
obtain and at confidence limit. We conclude that EDE is a viable
solution to the Hubble tension.Comment: 6 pages, 3 figures, 1 tabl
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