Withdrawn paper: fast multiplication of integer matrices

THIS PAPER HAS BEEN WITHDRAWN. We briefly discuss the error which was made in the original version of the withdrawn paper. Original abstract: in this paper we will show that dense n×n matrices with integer coefficients of bit sizes ⩽b can be multiplied in quasi-optimal time. This shows that the exponent ω_ℤ for matrix multiplication over ℤ is equal to two. Moreover, there is hope that the exponent can be observed in practice for a sufficiently good implementation