ISBN-13: 9783540694908 / Angielski / Twarda / 2008 / 614 str.
ISBN-13: 9783540694908 / Angielski / Twarda / 2008 / 614 str.
I never heard of Ugli?cation, Alice ventured to say. What is it? Lewis Carroll, Alice in Wonderland Subject and motivation. The present book is devoted to a theory of m- tipliers in spaces of di?erentiable functions and its applications to analysis, partial di?erential and integral equations. By a multiplier acting from one functionspaceS intoanotherS, wemeanafunctionwhichde?nesabounded 1 2 linear mapping ofS intoS by pointwise multiplication. Thus with any pair 1 2 of spacesS, S we associate a third one, the space of multipliersM(S?S ) 1 2 1 2 endowed with the norm of the operator of multiplication. In what follows, the role of the spacesS andS is played by Sobolev spaces, Bessel potential 1 2 spaces, Besov spaces, and the like. The Fourier multipliers are not dealt with in this book. In order to emp- size the di?erence between them and the multipliers under consideration, we attach Sobolev s name to the latter. By coining the term Sobolev multipliers we just hint at various spaces of di?erentiable functions of Sobolev s type, being fully aware that Sobolev never worked on multipliers. After all, Fourier never did either."