Another Mirror Cosmology Paper

One of the cleaner solutions in physics to the idea of the Big Bang in cosmology is one in which the universe extends infinitely forward and backward in time from the Big Bang. 

This could also explain the matter-antimatter asymmetry of the Universe is that an antimatter dominated universe extends backward in time (in our coordinate system) from the Big Bang and in which the arrow of time runs in the opposite direction due to entropy, which is the boundary between our matter dominated universe and the antimatter dominate universe on the other side of the Big Bang, 

This paper explores such a cosmology model from a mathematical physics perspective, in a way which embraces not only mirror cosmologies of the kind that I have suggested above, but also "bounce" cosmologies that do not posit an antimatter dominated and time reversed universe before the Big Bang. 

There could be quantum entanglement connections between the two sides of the Big Bang, but as the body text of the paper explains (at page 19), "quantum-entanglement correlations cannot be used to send a message from one world to the other: the arguments are essentially the same as those against faster-than-light communication from quantum entanglement."

In this model, the paper suggests that "the maximal energy density and curvature values are very large but finite (the typical energy scale may be the so-called Planck scale given by a combination of sqrt ((h-bar x c^5)/G) ≈ 1.22 × 10^19 GeV ≈ 1.42 × 10^32 Kelvin)."

We review the suggestion that it is possible to eliminate the Big Bang curvature singularity of the Friedmann cosmological solution by considering a particular type of degenerate spacetime metric. Specifically, we take the 4-dimensional spacetime metric to have a spacelike 3-dimensional defect with a vanishing determinant of the metric. 

This new solution suggests the existence of another "side" of the Big Bang (perhaps a more appropriate description than "pre-Big-Bang" phase used in our original paper). The corresponding new solution for defect wormholes is also briefly discussed.

F.R. Klinkhamer, "Big Bang as spacetime defect" arXiv:2412.03538 (Submitted December 4, 2024, last revised August 21, 2025, published version with expanded references) (31 pages).