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 <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:msup> <a:mi>e</a:mi> <a:mo>−</a:mo> </a:msup> <a:msup> <a:mi>e</a:mi> <a:mo>+</a:mo> </a:msup> </a:math> 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 <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:msub> <c:mi>α</c:mi> <c:mi>D</c:mi> </c:msub> <c:mo><</c:mo> <c:mn>4</c:mn> <c:mo>×</c:mo> <c:msup> <c:mn>10</c:mn> <c:mrow> <c:mo>−</c:mo> <c:mn>25</c:mn> </c:mrow> </c:msup> </c:math> .