On Equivalence and Linearization of Operator Matrix Functions with   Unbounded Entries
  In this paper we present equivalence results for several types of unbounded operator functions. A generalization of the concept equivalence after extension is introduced and used to prove equivalence and linearization for classes of unbounded operator functions. Further, we deduce methods of finding equivalences to operator matrix functions that utilizes equivalences of the entries. Finally, a method of finding equivalences and linearizations to a general case of operator matrix polynomials is presented. 
Christian Engstr\"om, Axel Torshage
math.FA