OK let's look at reality here. Anything on this earth can be formalized into a mathematical theory. That doesn't mean every formalization is accepted and accredited by academia.

This book has like three reviews on amazon and in general a formal theory doesn't exist. You won't find a formal theory about OOP calculi on wikipedia.

There are thousands of people in academia and of course at least one of them will attempt to formalize OOP. But largely said and done, overall there is no formal theory that is well accepted. Just random arbitrary attempts at formalization.