deletions | additions       diff --git a/We_can_calculate_its_dispersion__.tex b/We_can_calculate_its_dispersion__.tex  index d657877..83e0e13 100644  --- a/We_can_calculate_its_dispersion__.tex  +++ b/We_can_calculate_its_dispersion__.tex 
...
We can calculate its dispersion relation and get Fig.5. Only when $v=w$, the dispersion exhibits like a conductor. For any two band model, we can rewrite the Hamiltonian as $\textit{H(k)}=\textbf{d}(k)\hat{\sigma}$, where $d_x(k)=v+wcosk, d_y(k)=wsink, d_z(k)=0$. Define a winding number $v$, it counts the of times winds around the origin of $d_x,d_y$ plane. We call the case Fig.5(a) is trivial, and Fig.5(e) is topological.