# OhioLINKElectronic Theses & Dissertations Center

Search ETDs:
Hypercyclic Extensions of an Operator on a Hilbert Subspace with Prescribed Behaviors

2013, Doctor of Philosophy (Ph.D.), Bowling Green State University, Mathematics.
A continuous linear operator T : X → X on an infinite dimensional separable topological vector space X is said to be hypercyclic if there is a vector x in X whose orbit under T, orb(T, x) = {Tnx : n ≥ 0 } = { x, Tx, T2x, ..... } is dense in X. Such a vector x is said to be a hypercyclic vector for T. While the orbit of a hypercyclic vector goes everywhere in the space, there may be other vectors whose orbits are indeed finite and not contain a zero vector. Such a vector is called a periodic point. More precisely, we say a vector x in X is a periodic point for T if Tn x = x for some positive integer n depending on x. The operator T is said to be chaotic if T is hypercyclic and has a dense set of periodic points.

Let M be a closed subspace of a separable, infinite dimensional Hilbert space H with dim(H/M) = ∞ . We say that T : H → H is a chaotic extension of A : M → M if T is chaotic and T |M = A.

In this dissertation, we provide a criterion for the existence of an invertible chaotic extension. Indeed, we show that a bounded linear operator A : M → M has an invertible chaotic extension T : H → H if and only if A is bounded below. Motivated by our result, we further show that A : M → M has a chaotic Fredholm extension T : H → H if and only if A is left semi-Fredholm.

Our further investigation of hypercyclic extension results is on the existence of dual hypercyclic extension. The operator T : H → H is said to be a dual hypercyclic extension of A : M → M if T extends A, and both T : H → H and T* : H → H are hypercyclic. We actually give a complete characterization of the operator having dual hypercyclic extension on a separable, infinite dimensional Hilbert spaces. We show that a bounded linear operator A : M → M has a dual hypercyclic extension T : H → H if and only if its adjoint A* : M → M is hypercyclic.
Juan Bes (Committee Member)
So-Hsiang Chou (Committee Member)
Rachel Reinhart (Committee Member)
81 p.