FYI, a cyclical universe must now wrestle with a new stellar evolution model where white dwarf stars, slowly age into black dwarf stars, and some go supernova. 'Physicists calculate when the last supernova ever will happen', https://phys.org/news/2020-08-physicists-supernova.html. You can read the phys.org report and more detail at the NASA ADS Abstract site.
My observation. This report shows the universe will continue to expand and follow the 2nd Law. White dwarfs can evolve into black dwarfs and some go supernova too. The end is heat death, not eternal inflation or cyclic universe stories. Those who advocate eternal inflation or cyclic universe will now have to confront the black dwarf calculations in this report. The NASA ADS Abstract, 'Black Dwarf Supernova in the Far Future', https://ui.adsabs.harvard.edu/abs/2020MNRAS.tmp.2391C/abstract, August 2020. "In the far future long after star formation has ceased the universe will be populated by sparse degenerate remnants, mostly white dwarfs, though their ultimate fate is an open question. These white dwarfs will cool and freeze solid into black dwarfs while pycnonuclear fusion will slowly process their composition to iron-56. However, due to the declining electron fraction the Chandrasekhar limit of these stars will be decreasing and will eventually be below that of the most massive black dwarfs. As such, isolated dwarf stars with masses greater than ∼1.2M☉ will collapse in the far future due to the slow accumulation of iron-56 in their cores. If proton decay does not occur then this is the ultimate fate of about 10^21 stars, approximately one percent of all stars in the observable universe. We present calculations of the internal structure of black dwarfs with iron cores as a model for progenitors. From pycnonuclear fusion rates we estimate their lifetime and thus delay time to be 10^1100 years..."
My observation. This report shows the universe will continue to expand and follow the 2nd Law. White dwarfs can evolve into black dwarfs and some go supernova too. The end is heat death, not eternal inflation or cyclic universe stories. Those who advocate eternal inflation or cyclic universe will now have to confront the black dwarf calculations in this report. The NASA ADS Abstract, 'Black Dwarf Supernova in the Far Future', https://ui.adsabs.harvard.edu/abs/2020MNRAS.tmp.2391C/abstract, August 2020. "In the far future long after star formation has ceased the universe will be populated by sparse degenerate remnants, mostly white dwarfs, though their ultimate fate is an open question. These white dwarfs will cool and freeze solid into black dwarfs while pycnonuclear fusion will slowly process their composition to iron-56. However, due to the declining electron fraction the Chandrasekhar limit of these stars will be decreasing and will eventually be below that of the most massive black dwarfs. As such, isolated dwarf stars with masses greater than ∼1.2M☉ will collapse in the far future due to the slow accumulation of iron-56 in their cores. If proton decay does not occur then this is the ultimate fate of about 10^21 stars, approximately one percent of all stars in the observable universe. We present calculations of the internal structure of black dwarfs with iron cores as a model for progenitors. From pycnonuclear fusion rates we estimate their lifetime and thus delay time to be 10^1100 years..."
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