Fischbacher, Christoph Stefan (2017) On the Theory of Dissipative Extensions. Doctor of Philosophy (PhD) thesis, University of Kent,. (KAR id:61093)
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Abstract
We consider the problem of constructing dissipative extensions of given dissipative
Firstly, we discuss the dissipative extensions of symmetric operators and give a suffcient condition for when these extensions are completely nonselfadjoint. Moreover,
Then, we consider operators A and \widetilde{A} that form a dual pair, which means that A\subset \widetilde{A}^*, respectively \widetilde{A}\subset A^* Assuming that A and (\widetilde{A}) are dissipative, we present a method of determining the proper dissipative extensions \widehat{A} of this dual pair, i.e. we determine all dissipative operators \widehat{A} such that A\subset \subset\widehat{A}\subset\widetilde{A}^* provided that D(A)\cap D(\widetilde{A}) is dense in H. We discuss applications to symmetric operators, symmetric operators perturbed by a relatively bounded dissipative operator and more singular differential operators. Also, we investigate the stability of the numerical ranges of the various proper dissipative extensions of the dual pair (A,\widetilde{A}).
dissipative. If there exists a dissipative operator (\widetilde{A}) such that A and \widetilde{A} form a dual
the case, we propose a construction of a dual pair (A_0,\widetilde{A}_0), where A_0\subset A and \widetilde{A}_0\subset\widetilde{A} such that A_K is a proper extension of (A_0,\widetilde{A}_0).
selfadjoint and sectorial extensions of positive symmetric operators as described by Birman, Krein, Vishik and Grubb.
We finish with a discussion of nonproper extensions: Given a dual pair (A,\widetilde{A}) that satisfies certain assumptions, we construct all dissipative extensions of A that have domain contained in D(\widetilde{A}^*). Applying this result, we recover Crandall and Phillip's description
a strictly positive closable quadratic form, we find a criterion for an arbitrary extension of A to be dissipative.
Item Type:  Thesis (Doctor of Philosophy (PhD)) 

Thesis advisor:  Wood, Ian 
Uncontrolled keywords:  Operator theory, extension theory, dissipative operators, differential operators 
Subjects:  Q Science > QA Mathematics (inc Computing science) 
Divisions:  Divisions > Division of Computing, Engineering and Mathematical Sciences > School of Mathematics, Statistics and Actuarial Science 
Depositing User:  Users 1 not found. 
Date Deposited:  30 Mar 2017 11:00 UTC 
Last Modified:  16 Feb 2021 13:44 UTC 
Resource URI:  https://kar.kent.ac.uk/id/eprint/61093 (The current URI for this page, for reference purposes) 
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