inflation. In many realistic examples of particle physics having more than one light scalar fields is quite natural, especially in the case of MSSM [91]. However, as we shall argue below that within MSSM there are only handful of such good candidates for a curvaton [134– 136] $^{104}$. In the original curvaton paradigm it was assumed that the curvaton is responsible for generating the entire curvature perturbations, and the perturbations arising from the inflaton component are subdominant [126, 129–131]. However, there are variants where both inflaton and curvaton can contribute to the curvature perturbations, see for instance [831, 832]. Irrespective of their origins the curvaton must possess the following properties: During inflation the Hubble expansion rate is: H$_{inf}$ ≫ m$_{ϕ}$ , where m$_{ϕ}$ is the effective mass of the curvaton. Since it does not cost anything in energy, therefore the quantum fluctuations are free to accumulate along a curvaton direction and form a condensate with a large VEV, ϕ$_{0}$ . During inflation, V ( φ ) ≫ V ( ϕ ), where φ is the inflaton here. After inflation, H ∝ t − $^{1}$, and the curvaton stays at a relatively large VEV due to large Hubble friction term until H ≃ m$_{ϕ}$ , when the curvaton starts oscillating around the origin with an initial amplitude ∼ ϕ$_{0}$ . From then on | ϕ | is redshifted by the Hubble expansion ∝ H ( t ) for matter dominated and ∼ H 3 / $^{4}$( t ) for radiation dominated Universe. The energy of the oscillating flat direction may eventually start to dominate over the inflaton decay products. Furthermore, the curvaton must not evaporate due to thermal interactions from the plasma already created by the inflaton decay products [136, 833]. The curvaton and the inflaton decay products can be weakly coupled, i.e. via non-renormalizable in- teractions. In such a case the curvaton can survive long enough and its oscillations can possibly dominate the energy density while decaying. It has been shown that 104 Sneutrino as a curvaton have been considered in Refs. [823–825], With an extension of MSSM, where right handed sneutrinos are introduced as SM gauge singlets. However sneutrino alone is not a D -flat direction, one must consider the D -term contribution of the potential also. There are also models of curvaton where the field is a pNGB [826–828], or the curvaton action follows that of a Dirac-Born-Infeld [829, 830]. However, it is uncertain how such models of curvaton would excite dominantly the SM degrees of freedom. 207 • Lightness of the curvaton: • Longevity of the curvaton and its dominance: