from gravipy import * # Define variables t, r, theta, phi = symbols('t, r, \\theta, \phi') a = Function("a")(t) x = Coordinates('\chi', [t, r, theta, phi]) k = Symbol("k") # Define the Metric Tensor Metric = diag(-1, a**2/(1-k*r**2), a**2 * r**2, a**2 * r**2*sin(theta)**2) g = MetricTensor('g', x, Metric) # Calculate the Christoffel Symbols Ga = Christoffel("Ga", g) # Calculate the Ricci Tensor Ri = Ricci("Ri", g) # Calculate the Einstein Tensor G = Einstein("G",Ri) # Print the 00 component of the Einstein Tensor print(G(1,1))