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The evaporation of Primordial Black Hole (PBH) via Hawking radiation influences the evolution of Inter Galactic Medium by heating up the latter and consequently affects the 21cm signal originated from the neutral Hydrogen atoms. In this work, we have considered EDGES observational data of 21cm line corresponding to cosmic dawn era to constrain the mass and the abundance of PBHs. In this context, two different PBH mass distributions namely, power law and lognormal mass distributions are considered to estimate the effects of PBH evaporation on the 21cm brightness temperature $T_{21}$. In addition to these two mass distributions, different monochromatic masses are also considered. The impacts of Dark Matter - baryon interactions on $T_{21}$ are also considered in this work along with the influences of PBH evaporation. Furthermore, adopting different monochromatic masses for PBHs, an attempt has been made to formulate a distribution for PBH masses by associating a probability weightage of the $T_{21}$ values (at $z \sim 17.2$), within the range given by EDGES experiment, with the calculated $T_{21}$ values for each of the PBH mass values. The distribution best suited for the present purpose is found to be a combination of an error function and Owen function. Allowed contours in the parameter space of (initial PBH mass-dark matter mass) are obtained., Comment: 17 pages, 9 figures

The EDGES experiment related to the observant of brightness temperature \(T_{21}\) of 21cm line arising from ground state of neutral Hydrogen atom, has shown an excess absorption feature ( \(− 500^ {+200}_{ − 500}\) mK) in \(T_{21}\) spectrum corresponds to the era of cosmic dawn (\(z \sim 17.2\)). In order to explain the observed excess trough of \(T_{21}\) we consider Interacting Dark Energy scenario (interaction of Dark Matter and Dark Energy) along with the scattering of baryon matter with Dark Matter. Three different Interacting Dark Energy (IDE) models are used and the viability of those models are tested in the context of EDGES experimental results. It is found that Dark Matter-Dark Energy interaction modifies the evolution process of the Universe and hence consequently affects the brightness temperature. Dark Matter-baryon interaction also affects the \(T_{21}\) temperature since baryon fluid would transfer heat to the colder Dark Matter due to the Dark Matter baryon collision. In addition we also give bounds on the model parameters of the IDE models and Dark Matter model from EDGES observational data. It is noted that Dark Matter-Dark Energy interaction enables to explore larger range of Dark Matter mass regimes that would satisfy the EDGES result.

We explore the perturbationsn in Dark Energy by taking the Slotheon field model. The Slotheon field model follows from the extra-dimensional DGP (Dvali, Gabadadze, and Porrati) model and based on the Galileon transformation in curved space time. In this model a scalar field \(\pi \) in DGP theory is subjected to a shift symmetry in such a way that the final theory is invariant under this shift symmetry in curved space time. We consider that the accelerated expansion and Dark Energy are driven by the scalar field \(\pi \) with a potential \(V(\pi )\). Then we explore the Dark Energy perturbations within the framework of this Slotheon model. Using these perturbations we compute the matter power spectrum.