Continuing the issue raised by Klaus 1 month ago, I have a question. Is there a unified Lagrangian that combines particle physics and general relativity? The answer probably is: we do not know.
So here is the next question: Did anybody ever state in writing that such a unified Lagrangian must exist?
Is there an argument in favor (or against)?
There are so many people working on string theory, on loop quantum gravity and on other ideas.
Did anybody working on any idea for unification ever claim that unification is achieved using a Lagrangian?
What are the expectations?