1. The problem statement, all variables and given/known data Given some dispersion relation for the tight binding approximation in 2D: e(k_x,k_y) = -2t_1[cos(k_x*a)+cos(k_y*a)]-4t_2[cos(k_x*a)cos(k_y*a)] Show that the density of states has a logarithmic singularity for some choice of parameters t_i. 2. Relevant equations g(e)de=g integral dS/(2*pi)^3 *1/|grad e(K)| 3. The attempt at a solution When it says logaritmic singularity is it referring to von hove singularity? First I expanded the cosines. -2t_1[2-k_x^2*a^2/2 -k_y^2*a^2/2] -4t_2[1+k_x^2*a^2 k_y^2*a^2 Then what do I do?