 Bose-Einstein condensate

Inward Bound by Abraham Pais (1988) page 282 shows how this can be generalized from the Maxwell-Boltzmann distribution

A Bose–Einstein condensate (BEC) is a state of matter that occurs at extremely low temperatures, close to absolute zero (0 K or -273.15 °C). It was predicted by the physicists Satyendra Nath Bose and Albert Einstein in the early 20th century.