Can plasma physics establish a significant bound on long-range dark matter interactions?

Dark matter has been theorized to be charged under its own “dark electromagnetism” (dark-EM). Under this hypothesis, dark matter can behave like a cold collisionless plasma of self-interacting dark matter particles and exhibit plasmalike instabilities with observational consequences. Using the results published in [], which studied the degree of slowdown between two interpenetrating e−e+ plasma clouds due to plasma instabilities, estimates of similar interactions for colliding “dark plasmas” are explored. Comparison with astronomical observations reveals strong new constraints on dark-EM with the dark electromagnetic self-interaction αD<4×10−25. Published by the American Physical Society 2025