So, I'm still a bit new to the realm of physics but I was discussing theorized particles with my professor the other day and came to the conclusion, if gravitons do exist, could anti-gravitons be an explanation for why the universe is expanding? I was reading around and came across a similar topic saying that for this particle to have an anti-gravity property, it would basically need negative energy/mass. Being that the Higs Boson is the particle that provides mass, could there possibly be an anti-Higs particle that could be a solution to this idea of needing negative energy? Therefore having an opposite effect of gravity? Or could it be possible under certain conditions, to have an inverse curvature of space time, similar to the curvature produced by matter interacting with space time to produce a similar effect? I understand this is all very theoretical considering gravitons have not been discovered, but nonetheless its an entertaining idea.