Science is the effort to provide natural explanations of natural phenomena. The truth of any scientific proposition rests ultimately upon how well it accounts for the observations it is trying to explain, and by how well it can predict the results of experiments and/or future observations.
Mathematics is not a branch of science. I think it has been called the handmaiden of science; not an appellation that would make any mathematician happy, I'm sure. Much of theoretical physics is more math than science. Until it connects with observation and explaining how the universe works, it has no direct scientific truth value (it is neither true nor false. Heisenberg [I believe it was he] once remarked after listening to a paper being presented that the paper wasn't even wrong, meaning that the proposition being presented could not be falsified). It may lead to valuable insights, and it might be a valuable reformulation of an existing theory; but if it makes no new predictions that can be tested and that differentiate it from existing theory, then either it is not a scientific proposition or it is not a new scientific proposition.