When studying the CFT of a complex fermion Ψ we know that if it's periodic, ie if
Ψ(σ1+2π,σ2)=Ψ(σ1,σ2)
then there is a doubly degenerate Ramond vacuum which I denote |±⟩.
The question is what happens if Ψ is real? Is there a Ramond vacuum at all? Is it still doubly degenerate? Why/why not?