The Bose-Einstein distribution arises in the study of integer-spin particles in physics. For real and
and
, a common unnormalized form is
|
(1)
|
The corresponding integral, also allowing complex ,
is given by
|
(2)
| |||
|
(3)
|
for real and
, or for
and
, where
is the real part of
,
is the gamma function,
is the Lerch transcendent,
and
is a polylogarithm (NIST DLMF, eqns. 25.12.15-16).
For real , the denominator vanishes at
and this ordinary improper
integral does not converge.