Ultrashort-Period Binaries, Gravitational Radiation, and Mass Transfer. I. The Standard Model, with Applications to WZ Sagittae and Z Camelopardalis

Gravitational-radiation losses, by reducing the scale size of the system, induce mass transfer in the U Geminorum cataclysmic variables at the observed rate. The systems evolve from those having periods 10h to the shortest period observed, , in times typically of a few billion years or less.