In the above I was referring to the BB as beginning from a "point" source and expanding outward from there. In that case the universe and/or space could have a globally expanding boundary beyond our observable horizon.
The above quote from my post is out of context. The qualifying text is as follows, "If as I suggested earlier that initial singularity were describe more as an undifferentiated volume of space, of any dimensions, similar in principal to a super saturated solution and the BB event was an initial disturbance resulting in differentiation,..."
First, our cosmic horizon is that portion of the universe observable from our frame of reference. It does not extend to the global limits of the universe in any model. We currently estimate that to be something like 13.6 billion light years.
As to the differentiation issue, I was describing an essentially steady state model consistent with a BB like initial event. If the universe were initially uniform, as "like" a supper saturated fluid, an event that disturbed that initially uniform state could result in a BB like creation of matter within space. Prior to the event, space and the universe would be uniform, no separations between matter and energy, and after the event, just as with a supper saturated solution, matter and energy could be separated or differentiated. While matter and energy could still be uniformly distributed, space or the universe would no longer be uniform as composed of a single uniform substance or energy. If the universe began in a state similar to a "perfect fluid" this would or could occur instantly throughout. If it were more like a "nearly" perfect fluid the event could expand out from its point of origin much like suggested in the conventional BB model.
Your above description is consistent at least in intent with current theory. However, we really do not know what was! We can only project back to some point of origin based on our interpretations of current observations. We do not see equal amounts of matter and antimatter today, in the universe. And while theory predicts that they should have been created in equal amounts, the same theory cannot explain the absence of equal amounts of matter and antimatter, today. This suggests at least some missing information or that current theory is only an approximation.
To this add that all of the experiments we conduct now are based on the physics of today, not the physics that existed at the moment of the BB. Even current BB models suggest a rapid expansion that would be inconsistent with physics as we understand it today. It may very well be that the existence of matter is required for the creation of antimatter, along with conditions that are not and have never existed globally, within the universe. We really do not know what the laws of physics were like during the BB event. All we know is what they seem to be today.
