In spite of physics terms in the title, this paper is purely mathematical.
Its purpose is to introduce triangulated categories related to singularities of
algebraic varieties and establish a connection of these categories with
D-branes in Landau-Ginzburg models.Comment: 24 pp., LaTeX, Dedicated to the blessed memory of Andrei Nikolaevich
Tyurin -- adviser and friend, version 2 (some minor changes), accepted to
Trudy Steklov Institut