TITLE: Definite integration and summation are \#P-hard AUTHORS: Leonid Gurvits & Warren D. Smith NECI, 4 Independence Way, Princeton NJ 08540 USA. ABSTRACT: We show that the common symbolic manipulation tasks of computing multiple partial derivatives, definite integration, and definite summation, are \#P-hard, i.e., at least as hard as counting the accepting input strings for any Turing machine that halts in polynomial time. KEYWORDS: multiple partial derivatives, definite integration, definite summation, symbolic manipulation tasks, \#P-completeness, permanents, Ryser's formula.