The Heavy Limit of Dark Matter

Dark matter is often assumed to consist of particles that weigh as much as a proton but interact like a neutrino. However, dark matter particles could be much heavier, as well as much less interacting. New work from a team of theorists explores the upper limit of mass with a dark matter candidate that they call Planckian interacting dark matter (PIDM). The researchers show that the PIDM model implies a large number of primordial gravitational waves, which could produce a detectable signal in forthcoming cosmic microwave background (CMB) observations.