Pi-stability on derived categories -- 
Tom Bridgeland, January 24, 2003

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I explain the notion of a stability condition on a derived
category T. This is an abstraction of Mike Douglas' notion of
Pi-stability for D-Branes in string theory. The set Stab(T) of all stability
conditions on a fixed category T is a complex manifold. I describe
this space in the case when T is the derived category of a K3 surface.