INFLATION-PHENO

The phenomenology of Inflation

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 Obiettivo del progetto (Objective)

'Inflationary cosmology as a theory of the very early universe remains a paradigm in search of a theory in which it is realized in a fully consistent manner. Observationally, we are currently confronted with a wealth of data that seems to confirm the simplest realizations of this paradigm. Theoretically, we are still searching for a convincing realization of inflation that consistently embeds itself into a parent theory that contains the Standard Model as a sub-sector.

Requiring the inflationary potential be tuned so that a sufficient amount of quasi-exponential expansion results is a delicate proposition at the loop level in any effective field theory (EFT) that contains the inflaton. To require that these parameters be consistent with efficient reheating to standard model particles is an even more delicate proposition. To consistently realize all possible constraints at the loop level in a model that embeds itself in a purported model of UV complete physics (such as string theory or some low energy supergravity theory) remains the challenge of the day for inflationary model building.

In spite of the vast number of models that seem to be degenerate regarding their predictions (with certain assumptions) of the observed properties of the cosmic microwave background (CMB) power spectrum, the next generation of CMB observations offers us the possibility of discriminating among these models through their predictions for the higher order moments of the CMB. Furthermore, relaxing some of the simplifying assumptions alluded to above (such as consistently treating heavy fields that couple to the inflaton in an EFT setup rather than truncating them outright) can yield features in the power spectrum that may be detected in upcoming observations.

This goal of Inflation-pheno is to initiate a systematic study of the imprints on CMB observables of concrete models of inflation and to scrutinize them against observations from upcoming CMB and 21 cm observations.'

Introduzione (Teaser)

There is observational evidence that our Universe underwent a phase of accelerated expansion sometime in its early history. But, until recently, the predictions of theories suggested by quantum gravity for this inflationary epoch fared poorly when compared with measurements of the cosmic microwave background.

Descrizione progetto (Article)

Though tremendously successful, the concept of inflation does not fit into the standard model of particle physics. The inflationary epoch was a consequence of nuclear force breaking away from the weak and electromagnetic forces that it was unified with at higher temperatures.EU-funded scientists explored its connection with fundamental physics such as string theory and effective field theory.

The efforts of the scientists working on the INFLATION-PHENO (The phenomenology of inflation) project concentrated on the phenomenology of inflation. Data from the Planck mission, the Wilkinson Microwave Anisotropy Probe (WMAP) and the Background Imaging of Cosmic Extragalactic Polarization (BICEP2) telescope were revisited.

Detection of primordial gravitational waves gave the team a diagnostic tool to scrutinise models against observational data. These ripples in cosmic microwave background offered a new window onto the early Universe. The re-analysis of observational data revealed signatures of a blue tensor tilt that contradicts the predictions of inflationary models.

Specifically, the power spectrum of the tensor background representing fluctuations of closed strings has a blue tilt. This feature distinguishes the string thermodynamic generation of primordial perturbations from the predictions of standard inflationary models. INFLATION-PHENO scientists also searched for fundamental theories that underlie inflationary models.

The possibility that inflation contributes to the strengthening of the gravitational force at very high energies was explored through collaborations developed during the INFLATION-PHENO project. Similar details have worked out in realistic calculations without making poorly justified assumptions. However, although inflation has many attractive features, it remains to be proven in particle physics experiments.