Abstract: | By modifying Beukers' proof of Apéry's theorem that is irrational, we derive criteria for irrationality of Euler's constant, . For , we define a double integral and a positive integer , and prove that with the following are equivalent: 1. The fractional part of is given by for some . 2. The formula holds for all sufficiently large . 3. Euler's constant is a rational number. A corollary is that if infinitely often, then is irrational. Indeed, if the inequality holds for a given (we present numerical evidence for and is rational, then its denominator does not divide . We prove a new combinatorial identity in order to show that a certain linear form in logarithms is in fact . A by-product is a rapidly converging asymptotic formula for , used by P. Sebah to compute correct to 18063 decimals. |