Finite volume effects in $B_K$ with improved staggered fermions
  We extend our recent unquenched ($N_f=2+1$ flavor) calculation of $B_K$ using improved staggered fermions by including in the fits the finite volume shift predicted by one-loop staggered chiral perturbation theory. The net result is to lower the result in the continuum limit by 0.6%. This shift is slightly smaller than our previous estimate of finite volume effects based on a direct comparison between different volumes. To include the finite volume effects in a reasonable time, we found it necessary to calculate them using Graphics Processing Units. 
Jangho Kim, Chulwoo Jung, Hyung-Jin Kim, Weonjong Lee, and Stephen R.   Sharpe
hep-lat hep-ph