function v = pk(a, b)

r = 0: 0.05 :1;
theta = 0: 2*pi/100 :2*pi;
X = r' * cos(theta);
Y = r' * sin(theta);

num = 1 - X.^2 - Y.^2;
denom = 2*pi*((X - a).^2 + (Y - b).^2);
v = num ./ denom;

surf(X,Y,v); shading flat
axis([-1 1 -1 1 0 5])
