This paper is concerned with quaternion-valued functions on the plane and operators which act on such functions. In particular, we investigate the space L(R,H) of square-integrable quaternion-valued functions on the plane and apply the recently developed Clifford-Fourier transform and associated convolution theorem to characterise the closed translation-invariant submodules of L(R,H) and its bo...

We extend the de Branges-Beurling theorem characterizing shift-invariant spaces boundedly contained in Hardy space of square-summable power series to full Fock over Cd. Here, is identified as Non-commutative (NC) Space Taylor several non-commuting variables. then proceed study lattice operations on NC kernels and operator-valued multipliers between vector-valued spaces. In particular, we demons...

In this paper we study the vector-valued analogues of several inequalities for Fourier transform. particular, consider Hausdorff–Young, Hardy–Littlewood, Paley, Pitt, Bochkarev and Zygmund. The Pitt include Hausdorff–Young Hardy–Littlewood state that transform is bounded from $$L^p({\mathbb {R}}^d,|\cdot |^{\beta p})$$ into $$L^q({\mathbb |^{-\gamma q})$$ under certain condition on $$p,q,\beta ...

We introduce two kinds of quasi-inner functions. Since every rationally invariant subspace for a shift operator SK on a vector-valued Hardy space H(Ω, K) is generated by a quasi-inner function, we also provide relationships of quasi-inner functions by comparing rationally invariant subspaces generated by them. Furthermore, we discuss fundamental properties of quasi-inner functions, and quasi-in...

An explicit construction characterizing the operator-valued Bergman inner functions is given for a class of vector-valued standard weighted Bergman spaces in the unit disk. These operator-valued Bergman inner functions act as contractive multipliers from the Hardy space into the associated Bergman space, and they have a natural interpretation as transfer functions for a related class of discret...

We give a brief survey of subnormality and hyponormality of Toeplitz operators on the vector-valued Hardy space of the unit circle. We also solve the following subnormal Toeplitz completion problem: Complete the unspecified rational Toeplitz operators (i.e., the unknown entries are rational Toeplitz operators) of the partial block Toeplitz matrix

We introduce two kinds of quasi-inner functions. Since every rationally invariant subspace for a shift operator SK on a vector-valued Hardy space H(Ω, K) is generated by a quasi-inner function, we also provide relationships of quasi-inner functions by comparing rationally invariant subspaces generated by them. Furthermore, we discuss fundamental properties of quasi-inner functions, and quasi-in...

This paper extends the theory of Zen spaces (weighted Hardy/Bergman on right-hand half-plane) to Hilbert-space valued case, and describes multipliers them; it is shown that methods H∞ control can therefore be extended certain weighted L2 input output spaces. Next, case retarded delay systems with operator-valued transfer functions analysed, dependence structure determined by developing an exten...

Debnath and De La Sen introduced the notion of set valued interpolative Hardy-Rogers type contraction mappings on b-metric spaces proved that a complete space, whose all closed bounded subsets are compact, mapping has fixed point. This article presents generalizations above results by omitting assumption compact.

Starting with a general formula, precise but difficult to use, for the adjoint of a composition operator on a functional Hilbert space, we compute an explicit formula on the classical Hardy Hilbert space for the adjoint of a composition operator with rational symbol. To provide a foundation for this formula, we study an extension to the definitions of composition, weighted composition, and Toep...