Non-local formulation of ghost-free bigravity theory

We study the ghost-free bimetric theory of Hassan and Rosen, with parameters $\beta_i$ such that a flat Minkowski solution exists for both metrics. We show that, expanding around this solution and eliminating one of the two metrics with its own equation of motion, the remaining metric is governed by the Einstein-Hilbert action plus a non-local term proportional to $W_{\mu\nu\rho\sigma} (\Box-m^2)^{-1}W^{\mu\nu\rho\sigma}$, where $W_{\mu\nu\rho\sigma}$ is the Weyl tensor. The result is valid to quadratic order in the metric perturbation and to all orders in the derivative expansion. This example shows, in a simple setting, how such non-local extensions of GR can emerge from an underlying consistent theory, at the purely classical level.Comment: 16 page

Unitarity and predictiveness in new Higgs inflation

In new Higgs inflation the Higgs kinetic terms are non-minimally coupled to the Einstein tensor, allowing the Higgs field to play the role of the inflaton. The new interaction is non-renormalizable, and the model only describes physics below some cutoff scale. Even if the unknown UV physics does not affect the tree level inflaton potential significantly, it may still enter at loop level and modify the running of the Standard Model (SM) parameters. This is analogous to what happens in the original model for Higgs inflation. A key difference, though, is that in new Higgs inflation the inflationary predictions are sensitive to this running. Thus the boundary conditions at the EW scale as well as the unknown UV completion may leave a signature on the inflationary parameters. However, this dependence can be evaded if the kinetic terms of the SM fermions and gauge fields are non-minimally coupled to gravity as well. Our approach to determine the model's UV dependence and the connection between low and high scale physics can be used in any particle physics model of inflation.Comment: 21+6 pages, 1 figure; final version accepted by the journal, improvements of section

Multi-center phase II trial of chemo-radiotherapy with 5-fluorouracil, leucovorin and oxaliplatin in locally advanced esophageal cancer

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Ram pressure feeding super-massive black holes

When supermassive black holes at the center of galaxies accrete matter (usually gas), they give rise to highly energetic phenomena named Active Galactic Nuclei (AGN). A number of physical processes have been proposed to account for the funneling of gas towards the galaxy centers to feed the AGN. There are also several physical processes that can strip gas from a galaxy, and one of them is ram pressure stripping in galaxy clusters due to the hot and dense gas filling the space between galaxies. We report the discovery of a strong connection between severe ram pressure stripping and the presence of AGN activity. Searching in galaxy clusters at low redshift, we have selected the most extreme examples of jellyfish galaxies, which are galaxies with long tentacles of material extending for dozens of kpc beyond the galaxy disk. Using the MUSE spectrograph on the ESO Very Large Telescope, we find that 6 out of the 7 galaxies of this sample host a central AGN, and two of them also have galactic-scale AGN ionization cones. The high incidence of AGN among the most striking jellyfishes may be due to ram pressure causing gas to flow towards the center and triggering the AGN activity, or to an enhancement of the stripping caused by AGN energy injection, or both. Our analysis of the galaxy position and velocity relative to the cluster strongly supports the first hypothesis, and puts forward ram pressure as another, yet unforeseen, possible mechanism for feeding the central supermassive black hole with gas.Comment: published in Nature, Vol.548, Number 7667, pag.30

Renormalization group independence of Cosmological Attractors

The large class of inflationary models known as α- and ξ-attractors gives identical cosmological predictions at tree level (at leading order in inverse power of the number of efolds). Working with the renormalization group improved action, we show that these predictions are robust under quantum corrections. This means that for all the models considered the inflationary parameters (ns,r) are (nearly) independent on the Renormalization Group flow. The result follows once the field dependence of the renormalization scale, fixed by demanding the leading log correction to vanish, satisfies a quite generic condition. In Higgs inflation (which is a particular ξ-attractor) this is indeed the case; in the more general attractor models this is still ensured by the renormalizability of the theory in the effective field theory sense

L’AIR nella pratica di una Autorità indipendente: l’esperienza dell’Autorità per l’energia elettrica e il gas di applicazione dell’AIR alla regolazione della qualità del servizio

In the last ten years Regulatory Impact Analysis has become the instrument providing groundwork for evidence-based regulatory decisions in most developed countries. However, to an increase in quantity, it did not correspond an increase in quality. In Italy, Regulatory Impact Analysis has been in place for ten years on paper, but in practice it has not been performed consistently. Of particular interest is the case of independent regulatory authorities, which have been required to apply Regulatory Impact Analysis since 2003. This paper explores how Regulatory Impact Analysis is carried out, by examining in depth how an individual case –on the Regulation for Quality of Service- was executed by the Autorità per l’energia elettrica e il gas. The aim is to provide a picture of the process leading to the final Regulatory Impact Analysis report, rather than just a study of its content. The case illustrates how Regulatory Impact Analysis, when properly employed, can be an important aid to the regulatory decision, not only by assessing ex ante the economic impacts of regulatory proposals in terms of costs, benefits and risks, but also opening the spectrum of policy alternatives and systematically considering stakeholder opinions as part of the decision-making process. This case highlights also several difficulties, analytical and process-related, that emerge in practical applications. Finally, it shows that the experience and expertise built by the regulatory authority over the years had a significant impact on the quality of the analysis