We present a description of the diagonal of several spaces in the polydisk. We also generalize some previously known contentions and obtain some new assertions on the diagonal map using maximal functions and vector valued embedding theorems, and integral representations based on finite Blaschke products. All our results were previously known in the unit disk.
For any holomorphic function f on the unit polydisk D n we consider its restriction to the diagonal, i.e., the function in the unit disc D ⊂ C defined by Diag f(z) = f(z, . . . , z), and prove that the diagonal map Diag maps the space Qp,q,s(D n ) of the polydisk onto the space Qbq p,s,n(D ) of the unit disk.