Anderson's double complex and gamma monomials for rational function fields

Abstract

We investigate algebraic \Gamma-monomials of Thakur's positive characteristic \Gamma-function, by using Anderson-Das double complex method of computing the sign-cohomology of the universal ordinary distribution. We prove that the \Gamma-monomial associated to an element of the second sign-cohomology of the universal ordinary distribution of \mathbb{F}_{q}(T) generates a Kummer extension of the Carlitz cyclotomic function field, which is also a Galois extension of the base field \mathbb{F}_{q}(T). These results are characteristic-p analogues of those of Deligne on classical \Gamma-monomials, proofs of which were given by Das using the double complex method. In this paper, we also obtain some results on e-monomials of Carlitz's exponential function.