Only one particule at the Beginning?

Question

At the Beginning of the Universe, at the Big-Bang, was there only one first particule, the Particule Zero-One, which subdivided extremely rapidely to give other particules and the world began to expand?

Comments

The Beginning of the Universe is not a Physics subject, but a matter of speculations. Physics deals always with small systems; otherwise there would not be place for observers and their experimental equipment.

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But the Big-Bang theory is a subject of Physics, it is an hypothesis; the zero-one particule is also another hypothesis...

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If you roll the time back, then everything (including observers) will be placed in one point. No one would be able to establish clocs and length standards.

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Problems with such a concept of the Big Bang (itself probably a badly coined expression) are: What exactly is a particule, in particular this mysterious initial one? Where does it come from? The very concept of such a "particule" seems to imply that there is an "outside" of the particule, because one tends to picture a tiny sphere against a canvas of empty something (which something cannot be space-time, as this should be inside the particule). My understanding is that the universe did not start in time, but together with time: space-time and its metric, which latter can be used to define the proper time of an observer, are within the universe and subject to its expansion (Robertson-Walker-Friedmann-Lemaitre).

I personally find this very nice:  https://arxiv.org/abs/1803.08930 (Boyle et al, Big Bang, CPT and neutrino dark matter). The issue of a "start" appears not to be so relevant there.