A Russian nuclear physicist flirts with the wife of his mathematician colleague and makes an important mathematical discovery, all during the Nazi invasion of the Soviet Union.
I had not heard of this important work of Soviet fiction, a criticism of the Stalinist era, until it was brought to my attention this evening at the Notre Dame math department's "fluid dynamics seminar". Several mathematicians were challenged by my presence to attempt to name a work of mathematical fiction not already on my list. Nearly all of the suggestions were ones I had already added (or already considered and rejected). Then, François Ledrappier proposed Life and Fate, specifically emphasizing the amazing mathematical discovery that the protagonist makes.
Of course, I have not yet had time to read the novel myself, but the little I can find out from its Wikipedia entry and from browsing it on Amazon.com confirm that it certainly should be included in my database of mathematical fiction.
Here is a brief passage from the portion of the novel where he makes his great discovery:
(quoted from Life and Fate)
His head had been full of mathematical relationships, differential equations, the laws of higher algebra, number and probability theory. These mathematical relationships had an existence of their own in some void quite outside the world of atomic nuclei, stars, and electromagnetic or gravitational fields, outside space and time, outside the history of man and the geological history of the earth. And yet these relationships existed inside his own head.
And at the same time his head had been full of other laws and relationships: quantum interactions, fields of force, the constants that determined the process undergone by nuclei, the movement of light, and the expansion and contraction of space and time. To a theoretical physicist, the processes of the real world were only a reflection of laws that had been born in the desert of mathematics. It was not mathematics that reflected the world; the world itself was a projections of differential equations, a reflection of mathematics.

