“…Here the critical point, z c , is determined as a solution of the equation, ε k (z c ) = 0, in the complex plane obtained by analytical continuation, t → z [30][31][32][33][34][35][36][37][38]. Similarly, if initially the system was in the excited state: |ψ k (0) = |u + (k, 0) , so that α k (0) = 0 and β k (0) = 1, the result of integration yields…”