https://upload.wikimedia.org/wikipedia/commons/0/00/Standard...
All particles can be generated from photons, vacuum interactions given sufficient energy.
All particles disintegrate into photons given sufficient energy and interaction with the properties of the vacuum.
Ergo early in the big bang there could only be photons.
How specifically does this theory fail?
I understand how a very, very short time after the big bang there were material particles but I am asking what about before that time.
I suspect it is ingrained materialism less than physics. Interact a photon with a quantum fluctuations you get a quark. Normally quantum interactions self-quiet through interactions with antiparticles. Perhaps the reason why there is something rather than nothing is that a great part of the photons in the universe were there from the beginning of time. So you have original photons interacting with the vacuum to produce the material world we see today. Had there not been a surplus of photons the quantum fluctuation that gave rise to the universe would have in all probability self-anihilated in an instant.
The typical assumption is that the very early universe was in thermal equilibrium, in which case the set of particles present at any given time depends only on the temperature, and not on initial conditions.