The D0-brane metric in N = 2 sigma models
  We investigate the physical metric seen by a D0-brane probe in the background geometry of an N=2 sigma model. The metric is evaluated by calculating the Zamolodchikov metric for the disc two point function of the boundary operators corresponding to the displacement of the D0-brane boundary. At two loop order we show that the D0 metric receives an $R^2$ contribution. 
Thomas Wynter