Rational functions

ratio of polynomial functions

In mathematics, the polylogarithm (also known as '''Jonquière's function, for Alfred Jonquière) is a special function of order and argument . Only for special values of does the polylogarithm reduce to an elementary function such as the natural logarithm or a rational function. In quantum statistics, the polylogarithm function appears as the closed form of integrals of the Fermi–Dirac distribution and the Bose–Einstein distribution, and is also known as the Fermi–Dirac integral or the Bose–Einstein integral'''. In quantum electrodynamics, polylogarithms of positive integer order arise in the c

'best' approximation of a function by a rational function of given order

möbius transformation generalized to rings other than the complex numbers