Invariant multicones for families of matrices

In this paper, we investigate sufficient conditions on the structure of the eigenspaces of a given finite family of matrices to assure the existence of an embedded pair of invariant multicones, which are the smallest and the biggest in a suitable and natural sense. Multicones, very similar structures to those known in the literature as 1-multicones, are quite natural generalizations of the classical cones. The conditions we find also suggest us a practical computational procedure for the actual construction of such invariant embedded pair

Four stellar populations and extreme helium variation in the massive outer-halo globular cluster NGC 2419

Recent work revealed that both the helium variation within globular clusters (GCs) and the relative numbers of first and second-generation stars (1G, 2G) depend on the mass of the host cluster. Precise determination of the internal helium variations and of the fraction of 1G stars are crucial constraints to the formation scenarios of multiple populations (MPs). We exploit multi-band Hubble Space Telescope photometry to investigate MPs in NGC 2419, which is one of the most-massive and distant GCs of the Galaxy, almost isolated from its tidal influence. We find that the 1G hosts the ~37% of the analyzed stars, and identified three populations of 2G stars, namely 2GA, 2GB, and 2GC, which comprise the ~20%, ~31% and ~12% of stars, respectively. We compare the observed colors of these four populations with the colors derived from appropriate synthetic spectra to infer the relative helium abundances. We find that 2GA, 2GB, and 2GC stars are enhanced in helium mass fraction by deltaY ~0.01, 0.06, and 0.19 with respectto 1G stars that have primordial helium (Y=0.246). The high He enrichment of 2GC stars is hardly reconcilable with most of the current scenarios for MPs. Furthermore, the relatively larger fraction of 1G stars (~37%) compared to other massive GCs is noticeable. By exploiting literature results, we find that the fractions of 1G stars of GCs with large perigalactic distance are typically higher than in the other GCs with similar masses. This suggests that NGC 2419, similarly to other distant GCs, lost a lower fraction of 1G stars.Comment: 10 pages, 8 figures, submitted to MNRAS January 22n

NEUTRINOS AND THE LARGE SCALE STRUCTURE OF THE UNIVERSE

Present-day cosmology is experiencing a rather exciting season, as many observations of unprecedented quality either have recently been performed or are just about to be carried out. In this framework, long-standing unsolved questions, such as the nature and dynamics of cold dark matter and dark energy, the laws of gravity on cosmological scales, and the detailed physics of gravitational collapse and galaxy formation, might finally be assessed and hopefully find some answers. However, to maximally extract information from such copious and precise data, theoretical modeling must join the effort and push predictions to higher levels of accuracy. In the present thesis, I investigate a number of aspects regarding the role of massive neutrinos in cosmology, considering in particular their effects on the Large Scale Structure of the universe. The presence of massive neutrinos leaves its trace on many cosmological observables, requiring us to carefully account for their effects in order not to introduce systematic errors in our theories, but also allowing us to set constraints on quantities such as the number of neutrino species, their total mass and mass hierarchy. For this reason, the study of cosmological neutrinos is not only encompassed within the boundaries of cosmology, but reaches out to fundamental physics. In the first part of my work, I present a new method to set the initial conditions for cosmological simulations that include massive neutrinos. I then move to the study of the clustering ratio (a cosmological probe that quantifies the clustering properties of the galaxy distribution) in the presence of neutrinos, assessing its constraining power using both current data (from SDSS) and a forecast of a Euclid-like survey. Finally I study the possible degeneracies between neutrino effects and the parameters introduced to account for the galaxy-matter bias in some state-of-the art models

Processing and Communication Delays in EWS: On the Performance of the Earthcloud Prototype

A Seismic Alert System (SAS), also called Earthquake Warning System (EWS) or Earthquake Early Warning System (EEW or EEWS), represents one of the most important measures that can be taken to prevent and minimize earthquake damage. These systems are mainly used to detect P-waves and the faster seismic waves and to subsequently trigger an alarm about the incoming S-waves, the slower and most dangerous seismic waves. In some cases, distributed systems are also able to alert some locations before the impending P-waves strike them. This paper presents Earthcloud, a cloud-based SAS that aims to provide all the former capabilities while retaining financial accessibility. Earthcloud first results, generated from four months of data acquisition, are compared with those coming from other systems. In particular, the paper focuses on processing and communication delays, showing how the Earthcloud new detection strategy may minimize delays. Although a thorough test campaign with more sensor nodes is needed to assess performance reliably, especially for highly dense urban scenarios, initial results are promising, with total latencies for Earthcloud always kept under the 1-second mark, despite being at the expense of solid magnitude estimation

Prognostic value of Iron, Nutritional Status Indexes and Acute Phase Protein in Acute Coronary Syndrome.

Background. The relation between the inflammatory status during unstable angina and nutritional parameters has not been well described. We sought to investigate the relation between the acute inflammatory status, as evaluated on the basis of high C-reactive protein (CRP) and serum amyloid A levels and laboratory indexes of iron and nutritional status in patients with unstable angina, and whether the variations in iron levels have a prognostic significance.Methods. The study population consisted of 98 patients admitted to our facility with unstable (group 1: 64 consecutive patients, 52 males, 12 females, mean age 66 \ub1 10 years) or stable angina(group 2: 34 patients, 30 males, 4 females, mean age 65 \ub1 9 years). The hemoglobin levels, the erythrocyte mean cell volume, serum iron levels, the increase in transferrin levels, the decrease in the percent transferrin saturation, ferritin levels, the nutritional status, and the CRP and serum amyloid A levels were measured.Results. On the basis of a CRP value > 1 mg/dl, 47 patients with unstable angina and 4 patients with stable angina were identified as having active inflammatory disease. The presence of inflammation was associated with significantly lower mean values of hemoglobin, erythrocyte mean cell volume, serum iron and transferrin levels, and percent transferrin saturation in comparison with patients without inflammation. A significant inverse correlation coefficient between a CRP level > 1 mg/dl and hemoglobin, transferrin levels and percent transferrin saturation was observed: the strongest correlation was with serum iron levels. The relative risk of total cardiac events was significantlygreater in patients with low serum iron levels than in those with high serum iron levels.Conclusions. Patients with acute inflammation present altered iron status indexes. Increased CRP levels and reduced serum iron levels are associated with a worse outcome in patients with unstable angina

Support of Safety Services through Vehicular Communications: The Intersection Collision Avoidance Use Case

Cooperative systems are based on the periodical exchange of standardized information, thanks to which vehicles can advertise their presence, position and the direction they are moving to, and execute sophisticated C-ITS applications that can detect potentially dangerous situations and properly react. The technological pillar, which must enable a Vehicular ad Hoc Network (VANET), is now being debated: the candidates are the traditional WiFi-based approach and the upcoming cellular one. The application effectiveness, however, depends not only on the technology, but also on how fast it is adopted and becomes widespread, i.e., the so-called technology Penetration Rate (PR). In this paper, simulation is used to evaluate the Intersection Collision Avoidance (ICA) application for both candidate technologies, and evaluated as a function of the technology PR.This work was partially supported by FCA through the DiVe project, by the C.A.R.S. center at Politecnico di Torino, and by the H2020 5G-TRANSFORMER project (Project ID 761536