While working on her PhD thesis involving the inflaton field, mathematical physicist Lakshmi Nayak receives a page of equations, apparently from her future self. When she fills in the gaps in the "proof", she finds she has a method for achieving fasterthanlight travel. Over her advisor's objections, she posts the formulas on a preprint repository. The responses from other researchers are critical, but soon she is also on the receiving end of politically motivated oppression, forcing her to leave research and seek a job in industry. Then, someone offers to build her an FTL spaceship based on her formulae.
I suppose someone could argue that Lakshmi Nayak is a physicist and that this isn't a work of mathematical fiction. I am certainly open to such arguments; sometimes it is not clear when something crosses over from being science fiction to mathematical fiction. However, the book itself keeps telling us that she is a mathematician. The cover itself says
(quoted from Beyond the Hallowed Sky: Book One of the Lightspeed Trilogy)
Mathematician Lakshmi Nayak receives a letter from her future self about fasterthanlight travel.

Also, when she meets someone as she is traveling to a job interview and stumbles over an explanation for why she is applying for industry positions, the friend says "Mathematics has many applications?" (and she happily agrees). Finally, when someone says that she has a funny definition of the word "obviously", she replies "We do, yes. Physicists and mathematicians."
As a work of mathematical fiction, the interest lies in the fact that is shows the power of mathematics (because a page of equations leads to an important practical discovery) and that the main mathematician character is female. But, there is more to the book than that. Like many of MacLeod's books, it is an exploration of political philosophy. There are also lots of other main characters, including a biologist who has made an unusual discovery and a British spy (who happens to be an android). 