Thermalised dark radiation in the presence of PBH: $\mathrm{\Delta }{\mathrm{N}}_{\mathrm{eff}}$ and gravitational waves complementarity

Nayan Das, Suruj Jyoti Das, Debasish Borah

We study the possibility of detecting dark radiation (DR) produced by a combination of interactions with the thermal bath and ultra-light primordial black hole (PBH) evaporation in…