Three-dimensional flops and noncommutative rings

Abstract

For Y, Y+ three-dimensional smooth varieties related by a flop, Bondal and Orlov conjectured that the derived categories D-b (coh(Y)) and D-b (coh(Y+)) are equivalent. This conjecture was recently proved by Bridgeland. Our aim in this paper is to give a partially new proof of Bridgeland's result using noncommutative rings. The new proof also covers some mild singular and higher-dimensional situations (including those occuring in the recent paper by Chen [11]).