I will present a paradigm for the generation of the perturbations observed at the CMB where the deviations from homogeneity are not rooted in conventional QFT vacuum fluctuations of a scalar field (the inflaton) but rather in the intrinsic violations of homogeneities expected to unavoidably occur at the Planck scale in formulations of quantum gravity predicting discreteness of physics at the fundamental scale. If the universe undergoes a suitable phase of exponential expansion, such microscopic granularity (with an intrinsic scale: the Planck scale) can transfer inhomogeneities to the matter degrees of freedom in a way that produces an approximately scale invariant spectrum of perturbations (with no particular scale). Some assumptions are made about the physics close to the Planck scale but no assumptions about trans Planckian scales are necessary.
The main aim of the talk is to present a proof of concept showing an alternative perspective to the standard inflationary scenario where CMB features are directly linked to Planckian physics.
With some further assumptions (which will be explicitly mentioned) concerning the matter content of the universe and some natural initial conditions, the paradigm can be turned into a model producing results in agreement with observations and (what I believe are) additional appealing features.