In statistical thermodynamics, Bose-Einstein statistics determines the statistical distribution of identical indistinguishable bosons over the energy states in thermal equilibrium.
Bose-Einstein (or B-E) statistics are closely related to Maxwell-Boltzmann statistics (M-B) and Fermi-Dirac statistics (F-D). While F-D statistics holds for fermions, M-B statistics holds for "classical particles, i.e. identical but distinguishable particules, and represents the classical or high-temperature limit of both F-D and B-E statistics.
Bosons, unlike fermions, are not subject to the Pauli exclusion principle: an unlimited number of particles may occupy the same state at the same time. This explain why, at low temperatures, bosons can behave very differently than fermions; all the particles will tend to congregate together at the same lowest-energy state, forming what is known as a Bose-Einstein condensate.
B-E statistics was introduced for photons in 1920 by Bose and generalized to atoms by Einstein in 1924.
The distribution function f(E) is the probability that a particle is in energy state E, for B-E statistics the following hold:
The Bose-Einstein distribution function
where: