I will report our recent progress on the universal thermodynamic properties of conformal field theory (CFT), defined on a nonorientable minimal surface, the crosscapped disk (or real projective plane, RP2), with tensor network techniques. Through a cut-and-sew process, RP2 is topologically equivalent to a cylinder with a rainbow and a crosscap on two boundaries. We uncover that the crosscap contributes a fractional topological term 1/2 ln(k) in the free energy, with k a universal constant in two-dimensional CFT; while the rainbow boundary gives rise to a geometric term c/4  ln(beta), where beta is the surface size and c the central charge. Related universal thermal data on the Klein bottle and Mobius strip will also be briefly discussed in this talk.

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