Orthogonality and Mathematical Physics

The present work shows how the notion of perpendicularity, introduced and applied by Euclid in his "Elements" in the 3rd century BC, for which the sign " " has been used since 1634 firstly by the French mathematician Pierre Hérigone in one of his books, can be extended in Functional Analysis under the name of orthogonality, and how it can be applied in mathematical Physics. Knowledge in mathematical Analysis and functional Analysis are applied along the book. A special role is played by compact operators, applied in solving operatorial (integral) equations.

Autorentext

Prof. PhD Valter Olariu: PDEs; DEs; differential operators; mathematical Physics. Over 70 published scientific articles and 44 books. He was awarded by Romanian Ministry of Education. Prof. PhD Octav Olteanu: mathematical analysis; functional analysis; moment problem; polynomial approximation on unbounded subsets; 73 Journal articles and 16 books.