Well if you accept that cosmic expansion will have reddened the CMBR from what it was when it was emitted, then doesn't it have to be from a hot plasma?
a plasma of several baryons or enough to fill a universe all appearing at once, giving of radiation making them hot?
The time scales postulated in the big bang theory, are a little unbelievable for most normal people I think. I wonder how accurate the current mathematical model really is. It lacks repeatable experimental evidence.
Radiation would be given off during various stages of particle creation, as the universe
expands inflated, and became hot.
To try and reproduce particle creation experimentally would involve perhaps cooling space to near absolute zero perhaps, and see what happens ie wait. If baryons could be helped into existence, in a vacuum and become stable giving off a little measurable radiation perhaps. Then we might have experimental evidence for baryogenesis, from perhaps zero point energy.
I know Hoyle died still disbelieving in Big Bang theory, it has changed since his death, to include the inflationary stage etc. I wonder if he still would think it is a load of rubbish. I think it is reasonable to assume The big bang model time scales are an over simplification, assuming all matter appeared at once, it could be an ongoing thing as Hoyle suggested. Both would result in CMBR in an expanding universe covering a wide spectrum of red shifted frequencies.
The big bang model suggests a hot plasma beginning, if baryons came into existence with unstable properties they might lose energy through radiation. Not unlike muons decaying to electrons and radiation. The amount of radiation given off could be used to calibrate/confirm big bang models.
The current inflationary model of Linde suggests non uniform inflation to fix a few problems with Guths uniform inflation. https://en.wikipedia...ernal_inflation
Im off sailing again for a couple of weeks, so wont be posting for a while. Thanks for the input.