Unsurprising really. It seems fairly apparent that gravity merely influences the geometry of the substrate in which all known forms of matter & fundamental forces operate within. Something would have to seriously be fucky for antimatter to act counter to that geometry given it is comprised of similar particles with opposite charge. I’d assume astrophysicists know this, but wanted experimental proof for what seems to be straightforward logic from things we have experimentally confirmed.
The real question is what form does this geometry use to exert influence on the matter operating within curved spacetime? How is that information carried and how does gravity interface with that?
Antimatter is not just matter with an opposite charge. It’s matter with every type of charges (electromagnetic, strong and weak nuclear charges) inverted, as well as the “parity”, that is the relative direction of its spin compared to its propagation direction, are all inverted.
If you look for “CPT symmetry”, you’ll find better explanations than this.
It basically boils down to this: invert the flow of time, and every particle will look like antimatter, while antimatter will look like normal matter.
It would have been very likely that antimatter moved backwards in gravity of it was normal matter moving backwards in time!
There’s also no real reason for there to be more matter than antimatter in the universe. Any sufficiently high energy action will produce equal amounts of matter and antimatter, but there’s overwhelmingly more matter than antimatter floating around. It’s one of the big questions.
