Neutrino, γ\gamma-ray and cosmic ray fluxes from the core of the closest radio galaxies

The closest radio galaxies; Centaurus A, M87 and NGC 1275, have been detected from radio wavelengths to TeV $\gamma$-rays, and also studied as high-energy neutrino and ultra-high-energy cosmic ray potential emitters. Their spectral energy distributions show a double-peak feature, which is explained by synchrotron self-Compton model. However, TeV $\gamma$-ray measured spectra could suggest that very-high-energy $\gamma$-rays might have a hadronic origin. We introduce a lepto-hadronic model to describe the broadband spectral energy distribution; from radio to sub GeV photons as synchrotron self-Compton emission and TeV $\gamma$-ray photons as neutral pion decay resulting from p$\gamma$ interactions occurring close to the core. These photo-hadronic interactions take place when Fermi-accelerated protons interact with the seed photons around synchrotron self-Compton peaks. Obtaining a good description of the TeV $\gamma$-ray fluxes, firstly, we compute neutrino fluxes and events expected in IceCube detector and secondly, we estimate ultra-high-energy cosmic ray fluxes and event rate expected in Telescope Array, Pierre Auger and HiRes observatories. Within this scenario we show that the expected high-energy neutrinos cannot explain the astrophysical flux observed by IceCube, and the connection with ultra-high-energy cosmic rays observed by Auger experiment around Centaurus A, might be possible only considering a heavy nuclei composition in the observed events.Comment: 16 pages and 7 figures. Accepted for publication in Ap

On maximal inequalities for purely discontinuous martingales in infinite dimensions

The purpose of this paper is to give a survey of a class of maximal inequalities for purely discontinuous martingales, as well as for stochastic integral and convolutions with respect to Poisson measures, in infinite dimensional spaces. Such maximal inequalities are important in the study of stochastic partial differential equations with noise of jump type.Comment: 19 pages, no figure

Education-job (mis)matching and interregional migration: Italian university graduates’ transition to work

This paper explores the patterns of education-job (mis)matching of recent university graduates, focussing on the impact of interregional migration. With the aim of offering a place-based perspective on the topic, the paper looks at the three Italian macro-regions of the North, the Centre and the South, comparing them with the country as a whole. We use an indicator of education-job (mis)matching drawn and adapted from the literature, and apply both ordered logit and probit models with self-selection to a dataset on graduates’ entry in the labour market produced by the Italian National Statistical Institute. Our results suggest that, in line with most previous studies, interregional migration contributes to reduce education-job gaps: however, we find that the analysis for Italy as a whole masks stark differences between macro-regions, for which the typical North-South dualism still holds, confirming once more the cumulative and path-dependent nature of regional development trajectories

Graduate migration in Italy - Lifestyle or necessity?

This paper studies the locational choice of Italian mobile graduates, tackling simultaneously three aspects. First it analyses the structural drivers of migration (i.e. the key regional characteristics that attract high-skilled migrants) and the social structures that underpin it (i.e the role of migration networks). Secondly, it compares the preferences of migrants across Italy, to those who move from the least developed South to the Centre-North and those who move within the richer Centre-North. Thirdly, as graduate migration is a key mechanism to transfer knowledge from the university to the labour market, particular attention is given to migrants who are applying, in their jobs, exactly the skills gained through their degree. Results indicate that social networks are a much stronger determinant of the destination of graduates than regional characteristics, that to apply one’s knowledge it is necessary to move to highly innovative areas, and that graduates from different areas have different preferences and behaviour. In particular, whilst migration is a lifestyle choice for those who move within the Centre-North, it is driven by economic necessity for those who leave the South.

Variational inequalities in Hilbert spaces with measures and optimal stopping problems

We study the existence theory for parabolic variational inequalities in weighted $L^2$ spaces with respect to excessive measures associated with a transition semigroup. We characterize the value function of optimal stopping problems for finite and infinite dimensional diffusions as a generalized solution of such a variational inequality. The weighted $L^2$ setting allows us to cover some singular cases, such as optimal stopping for stochastic equations with degenerate diffusion coefficient. As an application of the theory, we consider the pricing of American-style contingent claims. Among others, we treat the cases of assets with stochastic volatility and with path-dependent payoffs.Comment: To appear in Applied Mathematics and Optimizatio

Ergodicity and Kolmogorov equations for dissipative SPDEs with singular drift: a variational approach

We prove existence of invariant measures for the Markovian semigroup generated by the solution to a parabolic semilinear stochastic PDE whose nonlinear drift term satisfies only a kind of symmetry condition on its behavior at infinity, but no restriction on its growth rate is imposed. Thanks to strong integrability properties of invariant measures $\mu$, solvability of the associated Kolmogorov equation in $L^1(\mu)$ is then established, and the infinitesimal generator of the transition semigroup is identified as the closure of the Kolmogorov operator. A key role is played by a generalized variational setting.Comment: 32 page

Well-posedness and asymptotic behavior for stochastic reaction-diffusion equations with multiplicative Poisson noise

We establish well-posedness in the mild sense for a class of stochastic semilinear evolution equations with a polynomially growing quasi-monotone nonlinearity and multiplicative Poisson noise. We also study existence and uniqueness of invariant measures for the associated semigroup in the Markovian case. A key role is played by a new maximal inequality for stochastic convolutions in $L_p$ spaces.Comment: Final versio