is shown as a function of s as a solid curve, for κ = 1/3. The triple dot-dashed curve is the approximation −(κs)²/32, the dot-dashed curve is −π(κs)/8 + 2 and the dashed curve is −π(κs)/8 + ln(κs/2)/2 + 0.9. Note that the function is initially Gaussian for small s but, although modified by the logarithm term, it is approximately linear for large s.