The Dark Universe: Primordial Black Hole $\leftrightharpoons$ Dark Graviton Gas Connection

Understand

We study the possible correspondence between 5-dimensional primordial black holes and massive 5-dimensional KK gravitons as dark matter candidate within the recently proposed dark dimension scenario that addresses the cosmological hierarchy problem.

• First, we show that in the local universe a population of 5-dimensional black holes with $M_{\rm BH}\sim 7\times 10^{13}~{\rm g}$ would be practically indistinguishable from a KK tower of dark gravitons with $m_{\rm DM} \sim 50~{\rm keV}$.
• Second, we connect the mass increase of 5-dimensional black holes and the related temperature decrease with the cooling of the tower of massive spin-2 KK excitations of the graviton.
• The dark gravitons are produced at a mass $\sim 1 - 50~{\rm GeV}$ and the bulk of their mass shifts down to roughly $1 - 100~{\rm keV}$ today.