N=4 Supersymmetric Yang-Mills Theory on Orbifold-$T^4/{\bf Z}_2$
  We derive the partition function of N=4 supersymmetric Yang-Mills theory on orbifold-$T^4/{\bf Z}_2$. In classical geometry, K3 surface is constructed from the orbifold-$T^4/{\bf Z}_2$. Along the same way as the orbifold construction, we construct the partition function of K3 surface from orbifold-$T^4/{\bf Z}_2$. The partition function is given by the product of the contribution of the untwisted sector of $T^4/{\bf Z}_2$, and that of the twisted sector of $T^4/{\bf Z}_2$ i.e., ${\cal O}(-2)$ curve blow-up formula. 
Masao Jinzenji (U. of Hokkaido), Toru Sasaki (U. of Hokkaido)