I am trying to do problem 5 at the following website: http://www.myoops.org/twocw/mit/NR/rdonlyres/Physics/8-251String-Theory-for-UndergraduatesSpring2003/F4BA42A3-4DD9-402F-BDA8-6D5CB14B0FAF/0/ps1.pdf [Broken] I got for (b) [tex] x' ~ \gamma \left( \gamma (1 -\beta^2) x'^0 + 2 \pi ( 1- \beta) R \right)[/tex] and I got a similar identification for ct'. For part (c), he wants us to find an identification in which the space coordinate is identified but the time coordinate is not. Does that mean is he asking to find x' ~ 0? x' ~ x' ? By using B_s as a variable and holding everything else constant?