Extension Theory of Symmetric Operators and Boundary Value Problems

This book presents the results obtained by the authors over the last four decades in the extension theory of symmetric operators in Hilbert spaces. First, some classic results are highlighted, influenced primarily by Krein, Vishik and Birman. Then, the method of boundary triples is discussed, demonstrating the universal character of the Weyl function which arises naturally both in problems of mathematical physics and classical interpolation problems. Readers of this book will gain an insight into the impressive construction of extension theory and its applications to problems in mathematical physics and analysis.