On the expansion of the Kummer function in terms of incomplete Gamma functions
Morosi, Carlo ; Pizzocchero, Livio
arXiv, 0304027 / Harvested from arXiv
Text on arXiv
The expansion of Kummer's hypergeometric function as a series of incomplete Gamma functions is discussed, for real values of the parameters and of the variable. The error performed approximating the Kummer function with a finite sum of Gammas is evaluated analytically. Bounds for it are derived, both pointwisely and uniformly in the variable; these characterize the convergence rate of the series, both pointwisely and in appropriate sup norms. The same analysis shows that finite sums of very few Gammas are sufficiently close to the Kummer function. The combination of these results with the known approximation methods for the incomplete Gammas allows to construct upper and lower approximants for the Kummer function using only exponentials, real powers and rational functions. Illustrative examples are provided.
Publié le : 2003-04-17
Classification:  Mathematical Physics,  Mathematics - Classical Analysis and ODEs,  33C15, 41AXX 
@article{0304027,
     author = {Morosi, Carlo and Pizzocchero, Livio},
     title = {On the expansion of the Kummer function in terms of incomplete Gamma
  functions},
     journal = {arXiv},
     volume = {2003},
     number = {0},
     year = {2003},
     language = {en},
     url = {http://dml.mathdoc.fr/item/0304027}
}

Morosi, Carlo; Pizzocchero, Livio. On the expansion of the Kummer function in terms of incomplete Gamma
  functions. arXiv, Tome 2003 (2003) no. 0, . http://gdmltest.u-ga.fr/item/0304027/