On 24 Sep 2015, at 15:13, 郭怀明 <hmguo@buaa.edu.cn> wrote:

Dear All,

  I have a question about the stiffness measured in direct loop QMC. I consider hard-core bosons, when the stiffness is the superfluid. I find its defination: <W^2_x+W^2_y>/2t\beta L, where W_x(y) is the winding number along the x or y direction. Suppose I have square lattice. If next nearest neighbor hopping is included with amplitude t', is its contribution is included in the code?

  Also if the lattice is two-leg ladder with NN and NNN hopping (the amplitudes are t and t'), the superfluid is along one direction. Is the contribution from the NN and NNN hoppings included?

Sincerely,

Huaiming Guo