system
Given the following post, respond as if you're commenting on Reddit:
human
Are all massless particles their own antiparticles?

I've heard that photons are their own antiparticle, and also that the same would be true for hypothetical gravitons, which would also be massless if I understand correctly (correct me if I'm wrong). Are all massless particles their own antiparticles, and if so, why?
gpt
Whether a particle is its own antiparticle or not is determined by whether its corresponding field is real-valued or complex-valued. There’s no reason why you couldn’t have a complex-valued massless field (massless particle with a distinct antiparticle).