Dark matter nugget and new early dark energy from interacting neutrino: A promising solution to Hubble anomaly. (arXiv:2005.11889v2 [astro-ph.CO] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Gogoi_A/0/1/0/all/0/1">Antareep Gogoi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Chanda_P/0/1/0/all/0/1">Prolay Chanda</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Das_S/0/1/0/all/0/1">Subinoy Das</a>
We present a novel scenario, in which light (mass $sim$ few rm{eV}) sterile
neutrinos interact with a dynamical scalar field and for some duration prior to
matter-radiation equality (MRE), the neutrino-scalar fluid behaves like early
dark energy (EDE) as the field adiabatically stays at minimum of effective
potential. In this scenario, when (sterile) neutrino becomes non-relativistic
before MRE, we show that, neutrino-scalar fluid develops instability in
perturbations followed by formation of neutrino-nuggets which redshifts like
cold dark matter. The sterile fermions get trapped in nuggets of degenerate
matter that are stable over cosmological timescales. As the scalar field
adiabaticaly relaxes into the minimum of an effective potential of
neutrino-scalar interaction, the early dark energy behaviour of the
neutrino-scalar fluid increases the local Hubble expansion rate and relaxes
Hubble anomaly. As neutrino mass scale is comparable to MRE temperature, the
duration and scale of this early DE happens naturally prior to recombination.
As it goes through an intermediate phase of nugget formation, we find that our
model does not worsen $S_8$ tension. As soon as the nugget forms, the neutrinos
decouple from the scalar field and the combined fluids no longer behave like
EDE, thus escaping the constraints from late time cosmology. The stability of
the dark matter nugget is achieved when the Fermi pressure balances the
attractive scalar force and we numerically find the mass and radius of nuggets
by solving the static configuration. We also show that the nugget lifetime can
be easily greater than the age of the Universe.
We present a novel scenario, in which light (mass $sim$ few rm{eV}) sterile
neutrinos interact with a dynamical scalar field and for some duration prior to
matter-radiation equality (MRE), the neutrino-scalar fluid behaves like early
dark energy (EDE) as the field adiabatically stays at minimum of effective
potential. In this scenario, when (sterile) neutrino becomes non-relativistic
before MRE, we show that, neutrino-scalar fluid develops instability in
perturbations followed by formation of neutrino-nuggets which redshifts like
cold dark matter. The sterile fermions get trapped in nuggets of degenerate
matter that are stable over cosmological timescales. As the scalar field
adiabaticaly relaxes into the minimum of an effective potential of
neutrino-scalar interaction, the early dark energy behaviour of the
neutrino-scalar fluid increases the local Hubble expansion rate and relaxes
Hubble anomaly. As neutrino mass scale is comparable to MRE temperature, the
duration and scale of this early DE happens naturally prior to recombination.
As it goes through an intermediate phase of nugget formation, we find that our
model does not worsen $S_8$ tension. As soon as the nugget forms, the neutrinos
decouple from the scalar field and the combined fluids no longer behave like
EDE, thus escaping the constraints from late time cosmology. The stability of
the dark matter nugget is achieved when the Fermi pressure balances the
attractive scalar force and we numerically find the mass and radius of nuggets
by solving the static configuration. We also show that the nugget lifetime can
be easily greater than the age of the Universe.
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