Abstract. In the simplest scenarios of the cosmic inflation the universe, at the very onset of its evolution, is almost empty filled with only a single scalar field, the inflaton, whose background energy density is responsible for the nearly exponential expansion of the universe and its quantum fluctuations, once stretched beyond the horizon scale, serve as the primordial seeds of clumpy universe we see today.

Although the predictions of this vanilla model is well compatible with current data ranging from CMB to LSS, there has been a continuing endeavour to study the consequence of presence of extra fields other than inflaton on those observables. In this talk, I am going to talk about possible footprints of light extra degrees of freedom during inflation on the primordial power spectrum of the curvature perturbations.