IAS Fundamental Physics Seminar Series - Constraints on Symmetric Dark Matter from Neutron Star Capture and Collapse

Abstract
Neutron stars are known to constrain asymmetric dark matter because accumulated particles can trigger collapse. The speaker will show that these constraints extend much further: even when dark matter is produced with equal particle and antiparticle abundances, the capture process inside a neutron star can become intrinsically asymmetric if the two species scatter off nucleons with slightly different strengths. This difference arises naturally from interference between interaction terms with specific charge-conjugation properties, and turns out to be generic across the full set of allowed dark matter–nucleon couplings. As a result, neutron stars can exclude extremely small scattering rates over a wide mass range, and the constraints remain effective even when the capture asymmetry is tiny. Neutron stars probe not only abundance asymmetries but also the microscopic structure of dark matter interactions, significantly broadening their impact on dark matter theory.