And most physical cosmologists recognize this and consider the failure to explain the beginning of real space and real time as a weakness of their theories, e.g. Steinhardt's cyclic, Hawking's imaginary time.
To find a closed cosmology, you must move away from the physical to the pure math or theology.
Max Tegmark's Level IV Parallel Universe is closed precisely because it is not physical, i.e. that what we perceive from a perspective inside 4D is a manifestation of mathematical structures which actually do exist outside of both space and time.
His cosmology is radical Platonism.
A Christian would not call it "mathematical structures" but Logos which is a Name of Jesus Christ, God the Creator. Logos is the Greek word which translates to Word and also to logic.
Rational reality means reality is logical. The fact that it is logical not only allows it to be described by mathematics; it allows it to exist!
Re: The geometric dimensions of this world apply to the physics of this world only, not to any other. If you are going to talk physics, keep in mind that the fact that this 4d world arose out of a more fundamental physics of higher dimension. It did not arise out of nothing as in the nonscientific claim of ex nihilo by virtue of the conservation of energy.
" One cannot project the math/physics of the present universe onto prior universes when it is convenient and then not, when it is not convenient."
There is no such projection. The fact that this universe has it's own gemetric structure, which differs from that from which it arose as a phase change, does not mean that 4d structure exits in the higher physics. It can be understood by noting this world appears as a phase change. That phase does not exist in the phase from which it changed from. The energy did though.
"most physical cosmologists recognize this and consider the failure to explain the beginning of real space and real time as a weakness of their theories, e.g. Steinhardt's cyclic, Hawking's imaginary time."
There is no general failure. The lack of knowledge refers to the particulars.
" To find a closed cosmology, you must move away from the physical to the pure math or theology."
No. Reality is reality and is neither math, nor theology, nor does it arise from either of those.
" Max Tegmark's Level IV Parallel Universe..., i.e. that what we perceive from a perspective inside 4D is a manifestation of mathematical structures which actually do exist outside of both space and time."
Nevertheless, those physical structures are a part of the 4d which arose as a phase change. Those "other structures" are not what they arose from.
"Logos which is a Name of Jesus Christ, God the Creator. Logos is the Greek word which translates to Word and also to logic."
God is a person. Logic is a set of objects with properties and the relationships between them. A person is not logic.
" In the beginning was the Word, and the Word was with God, and the Word was God. The same was in the beginning with God. All things were made by him; and without him was not any thing made that was made. In him was life; and the life was the light of men. – John 1:1-4"
This passage refers to a person. It says all things that were made were made by Him. It may be hard to grasp, but nevertheless, reality is and was not made.