It states that
“The proof requires the following assumptions:
The theory has a Lorentz-invariant Lagrangian.
The vacuum is Lorentz-invariant.
The particle is a localized excitation. Microscopically, it is not attached to a string or domain wall.
The particle is propagating, meaning that it has a finite, not infinite, mass.
The particle is a real excitation, meaning that states containing this particle have a positive-definite norm.”
So the question is Whether there is a generalization of it in curved spacetime？