Primordial black hole dark matter in the context of extra dimensions

Theories of large extra dimensions (LEDs) such as the Arkani-Hamed, Dimopoulos and Dvali scenario predict a "true" Planck scale M_⋆ near the TeV scale, while the observed M_{p l} is due to the geometric effect of compact extra dimensions. These theories allow for the creation of primordial black holes (PBHs) in the early Universe, from the collisional formation and subsequent accretion of black holes in the high-temperature plasma, leading to a novel cold dark matter (sub)component. Because of their existence in a higher-dimensional space, the usual relationship between mass, radius, and temperature is modified, leading to distinct behavior with respect to their four-dimensional counterparts. Here, we derive the cosmological creation and evolution of such PBH candidates, including the graybody factors describing their evaporation, and obtain limits on LED PBHs from direct observation of evaporation products, effects on big bang nucleosynthesis, and the cosmic microwave background angular power spectrum. Our limits cover scenarios of two to six extra dimensions, and PBH masses ranging from 10 to 10²¹ g . We find that for two extra dimensions, LED PBHs represent a viable dark matter candidate with a range of possible black hole masses between 10¹⁷ and 10²³ g depending on the Planck scale and reheating temperature. For M_⋆=10 TeV , this corresponds to PBH dark matter with a mass of M ≃10²¹ g , unconstrained by current observations. We further refine and update constraints on "ordinary" four-dimensional black holes.