About Subspace-Frequently Hypercyclic Operators

In this paper, we introduce subspace-frequently hypercyclic operators. We show that these operators are subspace hypercyclic and there are subspace-hypercyclic operators that are not subspace-frequently hypercyclic. There is a criterion like to subspace-hypercyclicity criterion that implies subspace-frequent hypercyclicity and if an operator T satisfies this criterion, then T ⊕ T is subspace-frequently hypercyclic. Additionally, operators on finite spaces can not be subspace-frequently hypercyclic.