A theory of generalized Donaldson-Thomas invariants

Understand

Let X be a Calabi-Yau 3-fold over C.

• The Donaldson-Thomas invariants of X are integers DT^a(t) which count stable sheaves with Chern character a on X, with respect to a Gieseker stability condition t.
• They are defined only for Chern characters a for which there are no strictly semistable sheaves on X.
• They have the good property that they are unchanged under deformations of X.