Bose–Einstein statistics, the quantum statistics applied to systems of particles with zero or integer spin (0, 1, 2... in units of ћ.). It was proposed in 1924 by the Indian physicist Sh. Bose for light quanta and extended in 1924 by A. Einstein to the molecules of ideal gases. In quantum mechanics the state of a system of particles is described by a wave function that depends on the coordinates and the spins of the particles. In the case of Bose–Einstein statistics the wave function is symmetric with respect to the interchange of any pair of identical particles (of their coordinates and spins). With such wave functions the occupation numbers of the quantum states are not restricted in any way, that is, any number of identical particles can be in one and the same state. For an ideal gas of identical particles the mean values of the occupation numbers are given by the Bose—Einstein distribution. For strongly rarefied gases Bose–Einstein statistics (like Fermi — Dirac statistics) goes over into Boltzmann statistics. (see Statistical physics).