Nearly invariant subspaces and kernels of Toeplitz operators on the Hardy space over the bidisk

In this paper, the analysis of nearly invariant subspaces and kernels of Toeplitz operators on the Hardy space over the bidisk is developed. Firstly, we transcribe Chalendar, Chevrot and Partington's result to vector-valued Hardy space H²_H(D) when H is an infinite dimensional separable complex Hilbert space. Secondly, we explore the definition of nearly invariant subspaces on Hardy space over the bidisk, and apply it to characterize kernels of Toeplitz operators. Finally, we define the nearly invariant subspaces for commutative isometric tuples, which allows us to show that the kernel of general Toeplitz operators is also nearly invariant.