On the symplectic structure of instanton moduli spaces
  We study the complex symplectic structure of the quiver varieties corresponding to the moduli spaces of SU(2) instantons on both commutative and non-commutative R^4. We identify global Darboux coordinates and quadratic Hamiltonians on classical phase spaces for which these quiver varieties are natural completions. We also show that the group of non-commutative symplectomorphisms of the corresponding path algebra acts transitively on the moduli spaces of non-commutative instantons.   This paper should be viewed as a step towards extending known results for Calogero-Moser spaces to the instanton moduli spaces. 
Roger Bielawski and Victor Pidstrygach