Resolving the Hubble Tension with New Early Dark Energy. (arXiv:2006.06686v3 [astro-ph.CO] UPDATED)

<a href="http://arxiv.org/find/astro-ph/1/au:+Niedermann_F/0/1/0/all/0/1">Florian Niedermann</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sloth_M/0/1/0/all/0/1">Martin S. Sloth</a>

New Early Dark Energy (NEDE) is a component of vacuum energy at the electron

volt scale, which decays in a first-order phase transition shortly before

recombination [arXiv:1910.10739]. The NEDE component has the potential to

resolve the tension between recent local measurements of the expansion rate of

the Universe using supernovae (SN) data and the expansion rate inferred from

the early Universe through measurements of the cosmic microwave background

(CMB) when assuming $Lambda$CDM. We discuss in depth the two-scalar field

model of the NEDE phase transition including the process of bubble percolation,

collision, and coalescence. We also estimate the gravitational wave signal

produced during the collision phase and argue that it can be searched for using

pulsar timing arrays. In a second step, we construct an effective cosmological

model, which describes the phase transition as an instantaneous process, and

derive the covariant equations that match perturbations across the transition

surface. Fitting the cosmological model to CMB, baryonic acoustic oscillations

and SN data, we report $H_0 = 69.6^{+1.0}_{-1.3} , textrm{km},

textrm{s}^{-1}, textrm{Mpc}^{-1}$ $(68 %$ C.L.) without the local

measurement of the Hubble parameter, bringing the tension down to $2.5,

sigma$. Including the local input, we find $H_0 = 71.4 pm 1.0 ,

textrm{km}, textrm{s}^{-1}, textrm{Mpc}^{-1}$ $(68 %$ C.L.) and strong

evidence for a non-vanishing NEDE component with a $simeq 4, sigma$

significance.

New Early Dark Energy (NEDE) is a component of vacuum energy at the electron

volt scale, which decays in a first-order phase transition shortly before

recombination [arXiv:1910.10739]. The NEDE component has the potential to

resolve the tension between recent local measurements of the expansion rate of

the Universe using supernovae (SN) data and the expansion rate inferred from

the early Universe through measurements of the cosmic microwave background

(CMB) when assuming $Lambda$CDM. We discuss in depth the two-scalar field

model of the NEDE phase transition including the process of bubble percolation,

collision, and coalescence. We also estimate the gravitational wave signal

produced during the collision phase and argue that it can be searched for using

pulsar timing arrays. In a second step, we construct an effective cosmological

model, which describes the phase transition as an instantaneous process, and

derive the covariant equations that match perturbations across the transition

surface. Fitting the cosmological model to CMB, baryonic acoustic oscillations

and SN data, we report $H_0 = 69.6^{+1.0}_{-1.3} , textrm{km},

textrm{s}^{-1}, textrm{Mpc}^{-1}$ $(68 %$ C.L.) without the local

measurement of the Hubble parameter, bringing the tension down to $2.5,

sigma$. Including the local input, we find $H_0 = 71.4 pm 1.0 ,

textrm{km}, textrm{s}^{-1}, textrm{Mpc}^{-1}$ $(68 %$ C.L.) and strong

evidence for a non-vanishing NEDE component with a $simeq 4, sigma$

significance.

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