**Black Holes* as a possible source of Universal Dark Energy**

Previously I have written about the possibility of **primordial black holes** as the explanation for dark matter, and on the observational constraints around such a possibility.

*But maybe it is dark energy, not dark matter, that black holes explain. More precisely, it would be dark energy stars (or gravatars, or GEODEs) that are observationally similar to black holes.*

**Dark energy**

Dark energy is named thusly because it has negative pressure. There is something known as an equation of state that relates pressure to energy density. For normal matter, or for dark matter, the coefficient of the relationship, w, is zero or slightly positive, and for radiation it is 1/3.

If it is non-zero and positive then the fluid component loses energy as the universe expands, and for radiation, this means there is a cosmological redshift. The redshift is in proportion to the universe’s linear scale factor, which can be written as the inverse of the cosmological redshift plus one, by normalizing it to the present-day scale. The cosmological redshift is a measure of the epoch as well, currently z = 0, and the higher the redshift the farther we look back into the past, into the earlier years of the universe. Light emitted at frequency ν is shifted to lower frequency (longer wavelength) ν’ = ν / (1 + z).

Since 1998, we have known that we live in a universe dominated by dark energy (and its associated dark pressure, or negative pressure)…