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I will explain how Joyce's wall-crossing formulae for invariants
counting semistable objects in an abelian category A may be understood
as Stokes phenomena for a connection on the Riemann sphere taking value
in the Ringel-Hall Lie algebra of A.
This allows one in particular to interpret his holomorphic generating
functions as defining an isomonodromic family of such connections
parametrised by the space of stability conditions of A.
This is joint work with T. Bridgeland
(arXiv:0801.3974).
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