The early universe operated at unification energies (there was no electromagnetic, strong or weak nuclear?

Question

force) how can we predict how the universe should have formed with a poor understanding of GUT, unified field theory or a string theory?

Answer 1

We work backwards from experimental and observational data. We have theories of electromagnetics, the weak force, the strong force, and gravity which all work well for present time conditions. We then ask how these forces could be aspects of a single force and what evidence is there to support the notion that there was only one force at some prior time. The weak anda electromagentic forces were hinted at being unified through various particle decay schemes and the electro-weak theory eventually unified them. The storng forcce got added in later as more evidence hinted at a higher unification. Gravity is the outsider right now and unifying it remains an active area of research. String theory is the de jour approach but has some fuindamental problems - like predicting particles that we should have already observed, but in fact have not.

Answer 2

You can't predict something that already happened, by definition. It's called retrodiction. Anyway, the answer is that we cannot describe the universe so early in the big bang. Retrodictions about times before what's called the Planck time are considered speculation.