The JWST High Redshift Observations and Primordial Non-Gaussianity

Several bright and massive galaxy candidates at high redshifts have been recently observed by the James Webb Space Telescope. Such early massive galaxies seem difficult to reconcile with standard $\Lambda$ Cold Dark Matter model predictions. We discuss under which circumstances such observed massive galaxy candidates can be explained by introducing primordial non-Gaussianity in the initial conditions of the cosmological perturbations.Comment: 10 pages, 4 figure

Primordial black holes from inflation and quantum diffusion

Primordial black holes as dark matter may be generated in single-field models of inflation thanks to the enhancement at small scales of the comoving curvature perturbation. This mechanism requires leaving the slow-roll phase to enter a non-attractor phase during which the inflaton travels across a plateau and its velocity drops down exponentially. We argue that quantum diffusion has a significant impact on the primordial black hole mass fraction making the classical standard prediction not trustable.Comment: 25+12 pages, 12 figures. v3: Appendix added with comments in response to arXiv:1807.0905

Nonlinear Dynamic System Identification in the Spectral Domain Using Particle-Bernstein Polynomials

System identification (SI) is the discipline of inferring mathematical models from unknown dynamic systems using the input/output observations of such systems with or without prior knowledge of some of the system parameters. Many valid algorithms are available in the literature, including Volterra series expansion, Hammerstein–Wiener models, nonlinear auto-regressive moving average model with exogenous inputs (NARMAX) and its derivatives (NARX, NARMA). Different nonlinear estimators can be used for those algorithms, such as polynomials, neural networks or wavelet networks. This paper uses a different approach, named particle-Bernstein polynomials, as an estimator for SI. Moreover, unlike the mentioned algorithms, this approach does not operate in the time domain but rather in the spectral components of the signals through the use of the discrete Karhunen–Loève transform (DKLT). Some experiments are performed to validate this approach using a publicly available dataset based on ground vibration tests recorded from a real F-16 aircraft. The experiments show better results when compared with some of the traditional algorithms, especially for large, heterogeneous datasets such as the one used. In particular, the absolute error obtained with the prosed method is 63% smaller with respect to NARX and from 42% to 62% smaller with respect to various artificial neural network-based approaches

The call of nature. Three post-pandemic scenarios about remote working in Milan

In recent years remote working (RW) arrangements have increased in many countries, mainly because of the COVID-19 pandemic, which has also intensified the need for humans to live closer to nature. Within this context, the paper aims to discuss three possible future scenarios for the spread of RW by 2050, and how this could affect residential choices, people’s relationship with the natural environment, and thus the renewed role of large cities, small towns, and areas close to nature. A specific focus is placed on the city of Milan in northwest Italy. To give empirical foundations to our scenarios, we analyzed data for the year 2021. The first scenario we consider (the Gentrified City) implies the risk that Milan will become a gentrified city, thus pushing social and economic inequality. However, on the contrary, our data suggest that in Italy a potential pool of workers would leave the city and move to a small town or closer to nature if allowed to work remotely. This trend could lead to the second scenario (the Doughnut City), but data for Milan show that the share of those willing to leave Milan is lower than the national average, which can be explained by the good quality of offered services; thus, the city center is unlikely to empty due to RW. The desirable option would be represented by the third scenario: some remote workers move to intermediary cities (the Intermediary Cities scenario), reducing territorial disparities

The Genetic resistence to Coccidia in Appenninica sheep

The study was conducted on a single herd of Appenninica sheep breed situated in Tuscany (Italy) from April to November 2004 on 108 sheep with the aim to identify the most resistant subjects to Coccidia. Moreover, the presence of gastro-intestinal Strongylids, Dicrocoelium sp. Moniezia spp.Strongyloides sp. and Trichuris sp. was also evaluated. Sheep selection may be based on OPG in adults animals, as it appears to be an indicator of sheep resistance to Coccidia. Before incorporating the parameter into breeding programmes, however, it is necessary to better appraise the degree of infestation of the other parasites as it may be difficult to select simultaneously for resistance to Coccidia and Strongylids unless the genetic correlation between these two traits is calculated and a selection index approach is used

Squeezed tensor non-Gaussianity in non-attractor inflation

We investigate primordial tensor non-Gaussianity in single field inflation, during a phase of non-attractor evolution when the spectrum of primordial tensor modes can be enhanced to a level detectable at interferometer scales. Making use of a tensor duality we introduced in arXiv:1808.10475, we analytically compute the full bispectrum of primordial tensor fluctuations during the non-attractor era. During this epoch the shape of the tensor bispectrum is enhanced in the squeezed limit, its amplitude can be amplified with respect to slow-roll models, and tensor non-Gaussianity can exhibit a scale dependence distinctive of our set-up. We prove that our results do not depend on the frame used for the calculations. Squeezed tensor non-Gaussianity induces a characteristic quadrupolar anisotropy on the power spectrum of the stochastic background of primordial tensor perturbations. As a step to make contact with gravitational wave experiments, we discuss the response function of a ground based Michelson interferometer to a gravitational wave background with such a feature.Comment: 34 pages, 4 figure

Inflation and Dark Energy from spectroscopy at z > 2

The expansion of the Universe is understood to have accelerated during two epochs: in its very first moments during a period of Inflation and much more recently, at z < 1, when Dark Energy is hypothesized to drive cosmic acceleration. The undiscovered mechanisms behind these two epochs represent some of the most important open problems in fundamental physics. The large cosmological volume at 2 < z < 5, together with the ability to efficiently target high-$z$ galaxies with known techniques, enables large gains in the study of Inflation and Dark Energy. A future spectroscopic survey can test the Gaussianity of the initial conditions up to a factor of ~50 better than our current bounds, crossing the crucial theoretical threshold of $\sigma(f_{NL}^{\rm local})$ of order unity that separates single field and multi-field models. Simultaneously, it can measure the fraction of Dark Energy at the percent level up to $z = 5$, thus serving as an unprecedented test of the standard model and opening up a tremendous discovery space