01308nas a2200133   4500008004100000245005300041210005000094260001300144520090800157100001601065700002001081700002201101856005101123       2014                        en  d00aN = 2 Quiver Gauge Theories on A-type ALE Spaces0 aN 2 Quiver Gauge Theories on Atype ALE Spaces  bSpringer3 aWe survey and compare recent approaches to the computation of the partition functions and correlators of chiral BPS observables in N = 2 gauge theories on ALE spaces based on quiver varieties and the minimal resolution Xk of the Ak-1 toric singularity C2/Zk, in light of their recently conjectured duality with two-dimensional coset conformal field theories. We review and elucidate the rigorous constructions of gauge theories for a particular family of ALE spaces, using their relation to the cohomology of moduli spaces of framed torsion-free sheaves on a suitable orbifold compactification of Xk. We extend these computations to generic N = 2 superconformal quiver gauge theories, obtaining in these instances new constraints on fractional instanton charges, a rigorous proof of the Nekrasov master formula, and new quantizations of Hitchin systems based on the underlying Seiberg–Witten geometry.1 aBruzzo, Ugo1 aSala, Francesco1 aSzabo, Richard J.  uhttp://urania.sissa.it/xmlui/handle/1963/3471901457nas a2200133   4500008004300000245010800043210006900151520097900220100001901199700002301218700002201241700002401263856003601287       2007                        en_Ud  00aBlack Holes, Instanton Counting on Toric Singularities and q-Deformed Two-Dimensional Yang-Mills Theory0 aBlack Holes Instanton Counting on Toric Singularities and qDefor3 aWe study the relationship between instanton counting in N=4 Yang-Mills theory on a generic four-dimensional toric orbifold and the semi-classical expansion of q-deformed Yang-Mills theory on the blowups of the minimal resolution of the orbifold singularity, with an eye to clarifying the recent proposal of using two-dimensional gauge theories to count microstates of black holes in four dimensions. We describe explicitly the instanton contributions to the counting of D-brane bound states which are captured by the two-dimensional gauge theory. We derive an intimate relationship between the two-dimensional Yang-Mills theory and Chern-Simons theory on generic Lens spaces, and use it to show that the correct instanton counting is only reproduced when the Chern-Simons contributions are treated as non-dynamical boundary conditions in the D4-brane gauge theory. We also use this correspondence to discuss the counting of instantons on higher genus ruled Riemann surfaces.1 aGriguolo, Luca1 aSeminara, Domenico1 aSzabo, Richard J.1 aTanzini, Alessandro  uhttp://hdl.handle.net/1963/1888