Elliptic Algebra U_{q,p}(g^) and Quantum Z-algebras

A new definition of the elliptic algebra U_{q,p}(g^) associated with an untwisted affine Lie algebra g^ is given as a topological algebra over the ring of formal power series in p. We also introduce a quantum dynamical analogue of Lepowsky-Wilson's Z-algebras. The Z-algebra governs the irreducibility of the infinite dimensional U_{q,p}(g^)-modules. Some level-1 examples indicate a direct connection of the irreducible U_{q,p}(g^)-modules to those of the W-algebras associated with the coset g^ \oplus g^ \supset (g^)_{diag} with level (r-g-1,1) (g:the dual Coxeter number), which includes Fateev- Lukyanov's WB_l-algebra.