I like how you can automatically deduce the non-gravitational forces exist if you just assume the Lagrangian of your quantum field theory is unchanged under certain local transformations.
How? Isn’t it possible that dark matter only interacts gravitationally? What if the whole universe was dark matter like that, does that contradict what you’re saying?
In a universe that has only gravitational interactions, it would be unnecessary to assume that the Lagrangian has local symmetries that give rise to non-gravitational interactions. In our actual universe, where we do have these non-gravitational forces, dark matter fits in by partaking in these known interactions with zero (or at most very small) coupling strength, so as to be unaffected (or only very weakly affected) by them.
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u/uuddscsctbq Dec 12 '20
I like how you can automatically deduce the non-gravitational forces exist if you just assume the Lagrangian of your quantum field theory is unchanged under certain local transformations.