2018-01-29 19:28:06 +0100 received badge ● Student (source) 2018-01-29 18:21:33 +0100 asked a question Pullback computation hanging I have the following code: M = Manifold(3, 'M') X. = M.chart() N = Manifold(3, 'N') XN. = N.chart() omega = N.diff_form(2) omega[0,1] = 2*b2/a^3 omega[0,2] = -2*b1/a^3 omega[1,2] = -2/a^2  Then I define a map M to N. r = sqrt(x^2+y^2+z^2) t = var('t', domain='real') STSa = r^(1/2)*(r*cosh(2*r*t) - z*sinh(2*r*t))^(-1/2) STSb1 = (x*sinh(2*r*t)/r)*STSa STSb2 = (y*sinh(2*r*t)/r)*STSa STS = M.diffeomorphism(N, [STSa, STSb1, STSb2])  Finally, I attempt to compute the pullback of omega to M by the map STS: s = STS.pullback(omega)  Unfortunately, the program runs and runs and nothing ever comes out. Can anyone identify the issue? Of course, the Jacobian of the map STS will not be very nice, but this pullback should be perfectly computable. 2018-01-29 18:21:33 +0100 asked a question Pullback computation is hanging. I have the following code: M = Manifold(3, 'M') X. = M.chart() N = Manifold(3, 'N') XN. = N.chart() omega = N.diff_form(2) omega[0,1] = 2*b2/a^3 omega[0,2] = -2*b1/a^3 omega[1,2] = -2/a^2  Then I define a map M to N. r = sqrt(x^2+y^2+z^2) t = var('t', domain='real') STSa = r^(1/2)*(r*cosh(2*r*t) - z*sinh(2*r*t))^(-1/2) STSb1 = (x*sinh(2*r*t)/r)*STSa STSb2 = (y*sinh(2*r*t)/r)*STSa STS = M.diffeomorphism(N, [STSa, STSb1, STSb2])  Finally, I attempt to compute the pullback of omega to M by the map STS: s = STS.pullback(omega)  Unfortunately, the program runs and runs and nothing ever comes out. Can anyone identify the issue? Of course, the Jacobian of the map STS will not be very nice, but this pullback should be perfectly computable.