Institute for Advanced Study/Princeton University Early Universe/Cosmology Lunch Discussion

Macroscopic Dark Matter (MDM) refers to an entire class of dark matter candidates, also commonly dubbed as Macros, consisting of composite objects characterized by a large mass and geo- metric cross-section. A possible signature of MDM is the capture of baryons from the cosmological plasma in the pre-recombination epoch, with the consequent injection of high-energy photons in the baryon-photon plasma. Without referring to any specific theoretical models, I will discuss the cosmological phenomenology of two distinct classes of Macros, composed either of ordinary matter or antimatter. In both scenarios, I will also analyze the impact of a non-vanishing electric charge carried by Macros. I will focus on the following probes of MDM: the change in the baryon density between the end of the Big Bang Nucleosynthesis (BBN) and the Cosmic Microwave Background (CMB) decoupling, the production of spectral distortions in the CMB and the kinetic coupling between charged MDM and baryons at the time of recombination. After discussing current constraints derived from the latest cosmological observations, I will show that future CMB spectral distortions experiments, like PIXIE and SuperPIXIE, would have the sensitivity to probe larger regions of the Macro parameter space: this would allow either for a possible evidence or for an improvement of the current bounds on Macros as dark matter candidates.