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Quantum Gravity Extension of the Inflationary Scenario

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A new cosmological theory tackles the description of the earliest era of the Universe, a period inaccessible by current models.
Quantum Gravity Extension of the Inflationary Scenario

An artist's image of the Big Bounce of Loop Quantum Cosmology, Luca Pozzi

Thanks to the space missions of the past two decades, we have entered the era of precision cosmology. A `standard' inflationary model of the early universe has emerged, which enjoys remarkable success in explaining the observed features of the cosmic background radiation. Yet the model is incomplete because it retains the Big Bang of general relativity where its underlying physics simply stops. One needs a quantum theory of gravity to go beyond Einstein and capture the true physics near the putative Big Bang. A promising avenue is provided by loop quantum gravity (LQG) where the Big Bang is naturally replaced by a Big Bounce and physics does not stop. This paper uses LQG to further extend our understanding of the very early cosmos. LQG suggests that the observable universe was homogeneous at the bounce except for the unceasing quantum fluctuations that cannot be gotten rid of even in principle. These are shown to evolve into the observed inhomogeneities in the background radiation which in turn serve as seeds for the large scale structure. Thus, the genesis of the cosmic structure is pushed back from the inflationary epoch all the way to the Big Bounce, covering some 11 orders of magnitude in matter density and curvature. In addition, there is a small window in the parameter space where the theory predicts new effects that could be observed in future missions.

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