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Report

Teaser, summary, work performed and final results

Periodic Reporting for period 1 - GEODESI (Theoretical and observational consequences of the Geometrical Destabilization of Inflation)

Teaser

Summary

The GEODESI project aims at interpreting current and forthcoming cosmological observations in a renewed theoretical framework about cosmological inflation, a primordial phase of the universe in which the latter expanded exponentially. The simplest toy models of inflation economically explain all current data, leaving no observational clue to guide theorists towards a finer physical understanding. In this context, the PI unveiled an hitherto unnoticed instability at play in the primordial universe that potentially affects all inflationary models and drastically modifies the interpretation of cosmological observations in terms of fundamental physics. The so-called Geometrical Destabilization of inflation reshuffles our understanding of the origin of structures in the universe and promises precision constraints on high-energy physics. It is crucial to develop this fresh look before a host of high-quality data from large-scale structure surveys and cosmic microwave background observations become available within the 5 year timescale of the project.

Work performed

The members of the GEODESI determined the fate of the geometrical destabilization of inflation, through numerical simulations and analytical works, reaching the conclusion that this phenomenon does not end inflation, but that the latter continues in an unusual manner. We studied this so-called sidetracked phase of inflation in detail, including the properties of the primordial density fluctuations it generates. New types of inflationary attractors have been identified, which offer interesting prospects for embedding inflation in realistic high-energy physics theories, and leave peculiar observational imprints, like unusual deviations from Gaussianity of the statistics of primordial fluctuations. This prompted us to revisit in more general terms than before the question of the non-Gaussianities generated from realistic models of inflation with multiple degrees of freedom. We have been also studying the consequences of the geometrical destabilization for the Higgs field during inflation, as well as the theoretical basis of the description of inflation by stochastic processes.

Final results

We have identified new types of inflationary attractors with strongly non-geodesic motion. They have attracted the attention of cosmologists and high-energy physicists as they offer the prospect of evading well-known constraints, and leave interesting observational signatures. In this context, we have also underlined the natural appearance of unusual effective field theories characterized by transient instabilities, which had been unexplored before and are now under scrutiny. Eventually, our results that revisit non-Gaussianities in models of inflation with multiple fields offer new insights on the cosmological collider program, and will be instrumental for interpreting future observational constraints with the required theoretical control.