Multipliers and equivalence of functions, spaces, and operators

This paper offers a unified approach to determining when two generalized Toeplitz operators on L^2 are equivalent. This will be done through multipliers between closed subspaces of L^2. Our discussion will include Toeplitz operators (and their duals) on the Hardy space, Hankel operators, asymmetric truncated Toeplitz operators, and dual asymmetric truncated Toeplitz operators. Along the way, there will be a discussion of equivalence of functions and kernels of generalized Toeplitz operators and a generalization of the Brown--Halmos theorem for this class of operators.