I Could Our Universe Be a Mirror Image of an Antimatter Universe?

[Anthony Beckwith]

"Our universe could be the mirror image of an antimatter universe extending backwards in time before the Big Bang. So claim physicists in Canada,"

https://physicsworld.com/a/our-univ...he-other-side-of-the-big-bang-say-physicists/

 

[fresh_42]

Here is the correct source:

ABSTRACT
We propose that the state of the Universe does not spontaneously violate CPT. Instead, the Universe after the big bang is the CPT image of the Universe before it, both classically and quantum mechanically. The pre- and postbang epochs comprise a universe-antiuniverse pair, emerging from nothing directly into a hot, radiation-dominated era. CPT symmetry selects a unique QFT vacuum state on such a spacetime, providing a new interpretation of the cosmological baryon asymmetry, as well as a remarkably economical explanation for the cosmological dark matter. Requiring only the standard three-generation model of particle physics (with right-handed neutrinos), a Z2 symmetry suffices to render one of the right-handed neutrinos stable. We calculate its abundance from first principles: matching the observed dark matter density requires its mass to be 4.8×108  GeV. Several other testable predictions follow: (i) the three light neutrinos are Majorana particles and allow neutrinoless double β decay; (ii) the lightest neutrino is massless; and (iii) there are no primordial long-wavelength gravitational waves. We mention connections to the strong CP problem and the arrow of time.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.251301

DOI:https://doi.org/10.1103/PhysRevLett.121.251301
https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.121.251301

 

[mathman]

Like all variations of multiverse theory, it is pure conjecture

 

[OCR]

In very broad terms, the fluctuations are due to the quantum-mechanical nature of space–time near the Big Bang singularity.

Oh, a multi-phasic temporal divergence in the space-time continuum... indeed, very interesting. .

.

 

[phyzguy]

Like all variations of multiverse theory, it is pure conjecture

But if I understand correctly, unlike most multiverse conjectures, this makes testable predictions, as detailed in the abstract.

 

[mathman]

But if I understand correctly, unlike most multiverse conjectures, this makes testable predictions, as detailed in the abstract.

I have trouble reading the abstract - I had an attack of MEGO.

 

[kimbyd]

I'm having difficulty understanding how this could work in practice.

They do have some testable predictions, which is definitely nice. Basically, if these testable predictions bear out, then it will be worth pursuing. I would break the predictions into two groups: two that can be detectable, and two that require non-detections which could be used to falsify the theory.

Detectable predictions:
1) A specific mass for the dark matter particle. So if we detect the dark matter particle and it has this mass, that would be exceptionally exciting.
2) A specific kind of nuclear decay (double beta decay with no neutrinos). There are lots of searches for this, but so far no result. This would have to be found to confirm the theory.

Non-detectable predictions (detection would falsify the theory):
1) No primordial gravity waves (no primordial B-mode polarization of the CMB, no direct detection of such waves).
2) No mass for the lightest neutrino.

With that out of the way, though, the theory is a bit confusing. It describes a singularity event which sends matter in the future and anti-matter into the past. It is true that such an event preserves CPT symmetry. But there's a problem: you can also describe such a universe as one that starts out as a collapsing universe (with matter) that then enters a bounce phase and re-expands, with the amount of matter conserved. The reason why it's a collapsing matter universe and not a collapsing anti-matter universe is because of the CPT symmetry: flip the arrow of time, and you also flip whether matter is considered anti-matter. But the choice of arrow of time is arbitrary in terms of the fundamental laws: all of the laws work with either choice. So the universe has to also solve the equations of motion if it's a collapsing matter universe which bounces and produces an expanding matter universe (with the same amount of matter).

With that description, how can they justify a universe which has arrows of time pointing away from the singular event in both directions? Such a concept completely messes with our concept of causality, because it implies some origination event in some kind of "super time". I don't have enough understanding of the particle physics to critique what they've done on that side of things, but I'm really not sure the cosmological/thermodynamic implications of such a universe make sense.