This book is de­ voted to some topical prob­ lems and various applica­ tions of Operator Theory and to its interplay with many other fields of analysis as modern approximation the­ ory, theory of dynamic sys­ tems, harmonic analysis and complex analysis. It consists of 20 carefully selected sur­ veys and research-expository papers. Their scope gives a representative status report on the field drawing a pic­ ture of a rapidly developing domain of analysis. An abun­ dance of references completes the picture. All papers included in the volume originate from lectures delivered at the l1th edition of the International Workshop on Operator The­ ory and its Applications (IWOTA-2000, June 13-16, Bordeaux). Some information about the conference, including the complete list of participants, can be found on forthcoming pages. The editors are indebted to A.Sudakov for helping them in polishing and assembling original TeX files. A. Borichev and N. Nikolski Talence, May 2001 v vii International Workshop on Operator Theory and Its Applications (June 13-June 16, 2000, Universite Bordeaux 1) The International Workshop on Operator Theory and its Applications (IWOTA) is a satellite meeting of the international symposium on the Mathe­ matical Theory of Networks and Systems (MNTS). In 2000, the MNTS is held in Perpignan, France, June 19-23. IWOTA 2000 was the eleventh workshop of this kind.