I have read this question:
As I understand, dark matter theoretically only interacts with the gravitational force, and doesn't interact with the other three fundamental forces: weak nuclear force, strong nuclear force, and electromagnetism.
There are a few questions on this site about dark matter annihilation and anti-dark matter, and all of them take it for granted that dark matter annihilates into photons.
Now as far as I understand, ordinary matter and anti-matter can annihilate into photons because ordinary matter does interact electromagnetically.
But dark matter does not interact electromagnetically, hence, dark matter cannot annihilate into photons, dark matter's energy cannot be transformed into the energy of the EM field.
- If dark matter can't interact electromagnetically, then how can it annihilate into photons?