Why doesn't light interact with dark matter?

Bobbywhy

Dark matter DOES interact with photons. In post # 7 of this thread I wrote “Of course light DOES interact with dark matter! Gravitational lensing is the most convincing evidence.”

In post # 8 Nabeshin remarked that “dark matter interacts gravitationally”

In my post #9 I reaffirmed the fact that Dark Matter does indeed interact with photons (light rays).

In post #10 Drakkith took issue with that statement.

In post #11 I elaborated, defined terms, made a statement of scientific fact, and concluded: “Therefore: Light interacts with dark matter.”

In post #12 Drakkith corrected his statement and wrote “Sorry, I meant "Doesn't interact with dark matter, other than gravity, at all.”

In post #15 Nabeshin, referencing my conclusion that dark matter interacts with light in post #11, agreed with my conclusion when he wrote “Eh, this is fine. I just don't want the OP to be confused and think dark matter couples to the electromagnetic force, that's all.”

Now, this:

I repeat: Dark Matter interacts with light rays (photons) during gravitational lensing.
If this is mistaken, will you please correct it with evidence to the contrary?
If it is accurate, will you please revise your post so as to clearly describe this natural process?

Thank you, Bobbywhy

Dickfore

Photons do not interact with anything during gravitational lensing. They follow the geodesics in curved space-time caused by the presence of matter/energy, and we interpret it as their deflection from the original path. But no event of absorption, and re-emission, whether its elastic or inelastic, of a photon took place during such a process. The gravitational interaction is not incorporated in the current scheme of interactions (the Standard Model), simply because it is not treated as a true force, but as a classical theory whose effect looks as a pseudoforce.

Drakkith

Bobby, everyone understands what is meant by "doesn't interact with". There is no reason to get bent out of shape.

Chronos

Yes, of course dark matter has a gravitational affect - how would we otherwise suspect its existence? Technicaly speaking, dark matter is thought to be weakly interactive [emphasis on weakly]. Detection of dark matter annihilations is an active area of research, although evidence to date suggests it is a rare occurence.

Steely Dan

Some current theories might say that, but let us not forget that our conjectures about dark matter are based on observational constraints from indirect inference rather than direct detection of dark matter particles. We do not have some firm reasoning motivated in fundamental physical theory like the Standard Model that predicts that dark matter particles do not couple to the electromagnetic field. Our prediction that dark matter does not interact electromagnetically is based on discrepancies between what we expect based on our knowledge of the gravitational field and what we observe in galaxies. So a more general response to the OP is that our best models of other physics place tight constraints on how strongly dark matter can participate in electromagnetic physics.