Primordial Non-Gaussianity and Primordial Tensor Modes

The discoveries in observational cosmology of the last two decades led to a tremendous progress in cosmology. From a theory with mainly qualitative ideas about the expanding universe originated from a state with high density and temper- ature (Hot Big Bang cosmological model), cosmology rapidly evolved to a quantita- tive science that culminated with the formulation of the so-called ΛCDM model in which the composition and the evolution of the universe are known well enough to make very detailed predictions for a large number of observables on many different scales. Nonetheless, the ΛCDM model lacks in giving a satisfactory explanation of the initial conditions that are necessary to explain the subsequent evolution of the uni- verse. The inflationary paradigm elegantly solves this problem, furthermore it pro- vides a solution for other issues that affect the standard cosmology such as the horizon and the flatness problems. Although the basic framework of inflationary cosmology is now well-established, the microphysical mechanism responsible for the accelerated expansion remains a mystery. In this thesis, we describe how the physics underlying inflation can be probed using the higher-order correlations of primordial density perturbations (non-Gaussianity). In particular, we focus on those correlation functions that involve primordial gravity waves (tensor modes). The importance of primordial tensor modes lies in their theoretical robustness: while scalar perturbations are sensitive to many details, tensor modes are much more model independent. In this thesis we start by stressing this robustness, focussing on tensor non-gaussianity. We show that in single-field models of inflation (i.e. within the framework of the Effective Field Theory of Inflation) the predictions for the correlation functions that involve tensor modes are pretty model independent: tensor bispectra can assume very few shapes. After having discussed the prediction of the simplest models we focus on the squeezed limit of the tensor-scalar-scalar 3-point function. The leading behaviour of this correlator is fixed by the so-called Tensor Consistency Relation in many inflationary theories. This model independent prediction is very robust and can be violated only in theories where there is an additional helicity-2 state besides the graviton or in models that enjoy a symmetry pattern different from the standard one. In the last part of this thesis we explore both these possibilities. First we intro- duce a set of rule that allow us to include light particles with spin in the Effective Field Theory of Inflation, then focussing on the phenomenology that arises from an additional light spin-2 field. Finally, we describe a model of inflation which is very peculiar and cannot be incorporated in the context of the Effective Field Theory of Inflation: Solid Inflation. Here the “stuff” that drives inflation has the same sym- metry as an ordinary solid. We show that even in solids some consistency relations among the non-gaussian correlators can still be derived

Natural theory of dark energy

We propose a mechanism that generates a naturally light dark energy field (with Hubble scale mass), starting from a theory with exclusively high scale (Planckian) couplings. It is derived from the clockwork model, with ${\cal O}(100)$ scalar fields interacting among themselves as well as with a 4-form field strength. We explicitly embed our model in type IIA supergravity. We also give an alternative interpretation in a braneworld set-up.Comment: Published version. 12 page

Probing higher-spin fields from inflation with higher-order statistics of the CMB

We investigate the degree to which the Cosmic Microwave Background (CMB) can be used to constrain primordial non-Gaussianity coming from the presence of spinning particles coupled to the inflaton. We compute the TTT and TTTT correlation functions arising from the exchange of a particle with spin s and generic mass, and the corresponding signal-to-noise ratios for a cosmic-variance-limited CMB experiment. We show that already with Planck data one could improve the theoretical bounds on the amplitude of these primordial templates by an order of magnitude. We particularly emphasize the fact that the trispectrum could be sizable even if the bispectrum is not, making it a prime observable to explore the particle content during inflation

Compact object scalarization with general relativity as a cosmic attractor

We demonstrate that there are theories that exhibit spontaneous scalarization in the strong gravity regime while having general relativity with a constant scalar as a cosmological attractor. We identify the minimal model that has this property and discuss its extensions

Dark energy loopholes some time after GW170817

We revisit the constraints on scalar tensor theories of modified gravity following the purge of GW170817. We pay particular attention to dynamical loopholes where the anomalous speed of propagation of the gravitational wave can vanish on-shell, when we impose the dynamical field equations. By working in the effective field theory formalism we are able to improve on previous analyses, scanning a much wider class of theories, including Beyond Horndeski and DHOST. Furthermore, the formalism is well adapted to consider the effect of inhomogeneous perturbations, where we explicitly take into account the fact that the galactic overdensities are pressureless to leading order

Persistent and transient olfactory deficits in COVID-19 are associated to inflammation and zinc homeostasis

IntroductionThe Coronavirus Disease 2019 (COVID-19) is mainly a respiratory syndrome that can affect multiple organ systems, causing a variety of symptoms. Among the most common and characteristic symptoms are deficits in smell and taste perception, which may last for weeks/months after COVID-19 diagnosis owing to mechanisms that are not fully elucidated. MethodsIn order to identify the determinants of olfactory symptom persistence, we obtained olfactory mucosa (OM) from 21 subjects, grouped according to clinical criteria: i) with persistent olfactory symptoms; ii) with transient olfactory symptoms; iii) without olfactory symptoms; and iv) non-COVID-19 controls. Cells from the olfactory mucosa were harvested for transcriptome analyses. Results and discussionRNA-Seq assays showed that gene expression levels are altered for a long time after infection. The expression profile of micro RNAs appeared significantly altered after infection, but no relationship with olfactory symptoms was found. On the other hand, patients with persistent olfactory deficits displayed increased levels of expression of genes involved in the inflammatory response and zinc homeostasis, suggesting an association with persistent or transient olfactory deficits in individuals who experienced SARS-CoV-2 infection

Science with the space-based interferometer LISA. IV: probing inflation with gravitational waves

We investigate the potential for the LISA space-based interferometer to detect the stochastic gravitational wave background produced from different mechanisms during inflation. Focusing on well-motivated scenarios, we study the resulting contributions from particle production during inflation, inflationary spectator fields with varying speed of sound, effective field theories of inflation with specific patterns of symmetry breaking and models leading to the formation of primordial black holes. The projected sensitivities of LISA are used in a model-independent way for various detector designs and configurations. We demonstrate that LISA is able to probe these well-motivated inflationary scenarios beyond the irreducible vacuum tensor modes expected from any inflationary background.Comment: 53 pages, 18 figures; v2: minor changes to match published versio

Type 1 Autoimmune Pancreatitis in Europe: Clinical Profile and Response to Treatment.

Background and aimsAutoimmune pancreatitis (AIP) is an immune-mediated disease of the pancreas with distinct pathophysiology and manifestations. Our aims were to characterize type 1 AIP in a large pan-European cohort and study the effectiveness of current treatment regimens.MethodsWe retrospectively analyzed adults diagnosed since 2005 with type 1 or not-otherwise-specified AIP in 42 European university hospitals. Type 1 AIP was uniformly diagnosed using specific diagnostic criteria. Patients with type 2 AIP and those who had undergone pancreatic surgery were excluded. The primary endpoint was complete remission, defined as the absence of clinical symptoms and resolution of the index radiological pancreatic abnormalities attributed to AIP.ResultsWe included 735 individuals with AIP (69% male; median age 57 years; 85% White). Steroid treatment was started in 634 patients, of whom 9 (1%) were lost to follow-up. The remaining 625 had a 79% (496/625) complete, 18% (111/625) partial, and 97% (607/625) cumulative remission rate, while 3% (18/625) did not achieve remission. No treatment was given in 95 patients, who had a 61% complete (58/95), 19% partial (18/95), and 80% cumulative (76/95) spontaneous remission rate. Higher (≥0.4 mg/kg/day) corticosteroid doses were no more effective than lower ( 2 weeks (OR 0.908; 95%CI 0.818-1.009). Elevated IgG4 levels were independently associated with a decreased chance of complete remission (OR 0.639; 95%CI 0.427-0.955). Relapse occurred in 30% of patients. Relapses within 6 months of remission induction were independent of the steroid tapering duration, induction treatment duration, and total cumulative dose.ConclusionPatients with type 1 AIP and elevated IgG4 level may need closer monitoring. For remission induction, a starting dose of 0.4 mg/kg/day for 2 weeks followed by a short taper period seems effective. This study provides no evidence to support more aggressive regimens

Primordial Non-Gaussianity and Cosmic Microwave Background Anomalies

L'analisi dei dati di Planck ha confermato alcune delle anomalie delle CHB trovate da WHAP, ed un livello simile di significanze statistiche. Tra queste anomalie c'è l'Hemispherical Power Asimmetry tra gli emisferi celesti nord e sud. L'obiettivo della tesi è di investigare la possibile connessione tra le anomalie delle CHB e la non-Gaussianità primordiale, da diversi punti di vista, spaziando tra vari modelli già proposti di non-Gaussianità primordiale