Bose-Einstein statistics.

This statistics was developed by S.N. Bose for light quanta, called photons and generalised by A.Einstein to describe the energy distribution among particles, whose spin angular momenta are nh where n=0,1,2,3,..... such particles are called bosons. wave  functions are symmetric on interchanging two bosons. The pauli exclusion principle which states that in each quantum state there cannot simultaneously be more than one particle, is not applicable to bosons, so that there is no upper limit to the number of bosons in a given quantum state.