Description
Irrationality measures of values of E-functions
E-functions are a class of special functions introduced by Siegel in 1929;
they include the exponential and Bessel functions. Values of E-functions at algebraic numbers are never Liouville : they are never extremely well approximated by rationals. If an E-function with rational coefficients is evaluated at a rational number, a more precise result holds : if irrational, the value has exponent of irrationality 2, like a randomly chosen number. This is a joint work with Tanguy Rivoal, based mostly on results of Shidlovsky, Chudnovsky, Andr ́e and Beukers.
