We establish a q-generalization of Gordon's theorem that the space of
diagonal coinvariants has a quotient identified with a perfect representation
of the rational double affine Hecke algebra. It leads to a simple proof of his
theorem and relates it to the Weyl algebras at roots of unity. The universal
double affine Hecke algebra and the corresponding universal double Dunkl
operators acting in noncommutative polynomials in terms of two sets of
variables are introduced.Comment: The final variant to appear in IMR
