I have a PhD in a social science discipline. I admit to not having your level of expertise. Nevertheless, I don't accept natural cause explanations for the universe being infinite. I have not found a science argument that closes all the loop holes. If you study such a theory long enough you will find deficiencies. No use discussing it further, it leads to a log jams. I have had some supernatural experiences which have informed about the nature of eternity. God and heaven is an entirely different reality, it does not resemble our dark, hostile universe. God created the universe as a prison for Satan. Knowing eternity can be a spark of bright white substance, I find no such matching entity in our universe. If the universe was infinity or eternal it would be heaven. I understand the nature of science is to constantly seek solutions. However, some things are impossible. You cannot create a condition, state of existence, or material substance, which is eternal, neither can you find it in the universe. No matter how advance the math, or the theory, it can never, and will never, be done. Only God is eternal.
The world "eternity" has been abused. I've heard Christians say, I will have eternal life in heaven. Not even angels have eternal lives, they had beginnings. You may say you will be immortal, which is partly correct. Immortality may be a condition for a creature's existence, but creatures always have a beginning. Only heavenly creatures live without an end. In heaven you may enjoy God's eternity, but only God is eternal. I think one reason for people getting it mixed up is arrogance. For some reason, they believe they are entitled to have god-like status. No matter how advanced or sophistical a theory, or the math, given an opportunity and enough time, I can critique it. I have an advantage, I know for certain God exists, and I know for certain heaven exists. In many ways, the universe is the anti-thesis to heaven, it is Satan's finite prison. God did not intend to put Satan in a prison without an end. Based on Satan's transgressions, God is generous to allow him so much time.