How sticky is the Universe?
All known physical fluids are a bit sticky. Syrup is very sticky.
Why this research?
Shut up 🤐 Understanding the Universe is important.
In standard approaches to cosmology, one does not consider the Universe to be sticky — at least not today. Rather, on large scales, it is modelled as a perfect fluid. But is the Universe really not sticky at all?
If I whirl the coffee in my mug around, the motion dies out after a few seconds, or minutes. When the wind stirs up the waters, the roaring of the waves is a secure sign that the motion is fading.
But with the Universe? Does the motion really never settle? Or.. is there at least not even the slightest dissipation of energy?
Surely there is. In viscous cosmology we investigate whether or not such energy-dissipation mechanisms is capable of shedding light on the dark sector of our Universe…
In a recent paper (to come out) we suggest that this could resolve the so-called H0-tension. The Hubble constant contains information about the rate of expansion of rhe Universe today, and can be measured in many different ways. Principally, there are two categories of measurements: (i) Those extrapolated from measurements of the afterglow from the big bang and (ii) more direct measurements from the local Universe around us. The problem is that these groups of measurements yield different values. We propose a solution through bulk viscosity.
Have a read:
[2006.09514] Remarks on cosmological bulk viscosity in different epochs (arxiv.org)
To appear (2021): Could bulk viscosity resolve the Hubble tension?