In this 2013 Nature article there is a short presentation of the causal dynamical triangulations approach to quantum gravity, where it is said
Intriguingly, the simulations also hint that soon after the Big Bang, the Universe went through an infant phase with only two dimensions — one of space and one of time. This prediction has also been made independently by others attempting to derive equations of quantum gravity, and even some who suggest that the appearance of dark energy is a sign that our Universe is now growing a fourth spatial dimension. Others have shown that a two-dimensional phase in the early Universe would create patterns similar to those already seen in the cosmic microwave background.
but unfortunately there are no references to who the "some" and "others" are. What are these theories where the number of spatial dimensions of the universe is not constant over its history?