The https://www-thphys.physics.ox.ac.uk/people/AndreiStarinets/TUTORIALS_NOTES_GR/gr-cosmology-exam-paper-2011-solutions.pdf#page=19[official notes, PDF p. 19, handwritten p. 12] integrate the radial <null geodesic>, express the radial coordinate in terms of <comoving distance>, and give its maximum value in that coordinate chart. The maximum radial coordinate is not the total path length around a closed spatial slice.

Solution

Past exam of the general relativity and cosmology and condensed matter physics paper of Part B of the physics course of the University of Oxford / 2011 / Section V / 3 / Unlettered 3 / Solution

 Solution (source code)