Wrong there is obvious proof. There are mathematical models that may suggest a multiverse. Therefore it is worth investigation. HOWEVER the only way any of these models would be accepted would be through experiment. Until then none will be accepted.
You clearly don't understand what the word "proof" means or you mean something different than me. To me "proof" is evidence and that must be observable, testable, measurable, repeatable and falsifiable.
I don't know what models you have looked at and I would like you to give an example of such a model, one I heard about goes something along the lines of; A multiverse could be a explanation of the big bang, mathematical formulas show how such a model would work and how the universe could have been formed under such conditions.
No evidence for a multiverse, no proof... But this is a hypothesis alongside many others.
There are ALSO tens of mathematical models that suggest a unified theory. So there is a mathematical evidence for these theories which merit investigation.
Study this a little and you will see that such "mathematical models" are by no means evidence. Or prove me wrong and link one that do.
Lets say we lived a few thousand years ago and we thought that everything had a God. And I came up with the hypnosis that the God of rain was in love with the God of the rainbow. I did many observations to show that this could be the case. This would not be proof, it would just be a way to explain what I saw.
It is the same way with these models, we come up with reasons for what we see, try to make sense of them with hypothesis, but the calculations that built the hypnosis is in no way evidence for that hypothesis...
There is no mathematical model as yet that suggests God. So why would it merit investigation?
I have no idea, you tell me.
I re-iterate: Atheism is scientific.
Atheism is in no way, shape or form science. Wikipedia it if you don't believe me... Neither is Theism, Deism or any other belief system.