Replica bounds for diluted non-Poissonian spin systems

In this paper we extend replica bounds and free energy subadditivity arguments to diluted spin-glass models on graphs with arbitrary, non-Poissonian degree distribution. The new difficulties specific of this case are overcome introducing an interpolation procedure that stresses the relation between interpolation methods and the cavity method. As a byproduct we obtain self-averaging identities that generalize the Ghirlanda-Guerra ones to the multi-overlap case.Comment: Latex file, 15 pages, 2 eps figures; Weak point revised and corrected; Misprints correcte

The radio lighthouse CU Virginis: the spindown of a single main sequence star

The fast rotating star CU Virginis is a magnetic chemically peculiar star with an oblique dipolar magnetic field. The continuum radio emission has been interpreted as gyrosyncrotron emission arising from a thin magnetospheric layer. Previous radio observations at 1.4 GHz showed that a 100% circular polarized and highly directive emission component overlaps to the continuum emission two times per rotation, when the magnetic axis lies in the plane of the sky. This sort of radio lighthouse has been proposed to be due to cyclotron maser emission generated above the magnetic pole and propagating perpendicularly to the magnetic axis. Observations carried out with the Australia Telescope Compact Array at 1.4 and 2.5 GHz one year after this discovery show that this radio emission is still present, meaning that the phenomenon responsible for this process is steady on a timescale of years. The emitted radiation spans at least 1 GHz, being observed from 1.4 to 2.5 GHz. On the light of recent results on the physics of the magnetosphere of this star, the possibility of plasma radiation is ruled out. The characteristics of this radio lighthouse provides us a good marker of the rotation period, since the peaks are visible at particular rotational phases. After one year, they show a delay of about 15 minutes. This is interpreted as a new abrupt spinning down of the star. Among several possibilities, a quick emptying of the equatorial magnetic belt after reaching the maximum density can account for the magnitude of the breaking. The study of the coherent emission in stars like CU Vir, as well as in pre main sequence stars, can give important insight into the angular momentum evolution in young stars. This is a promising field of investigation that high sensitivity radio interferometers such as SKA can exploit.Comment: Accepted to MNRAS, 8 pages, 7 figures, updated versio

Complexity transitions in global algorithms for sparse linear systems over finite fields

We study the computational complexity of a very basic problem, namely that of finding solutions to a very large set of random linear equations in a finite Galois Field modulo q. Using tools from statistical mechanics we are able to identify phase transitions in the structure of the solution space and to connect them to changes in performance of a global algorithm, namely Gaussian elimination. Crossing phase boundaries produces a dramatic increase in memory and CPU requirements necessary to the algorithms. In turn, this causes the saturation of the upper bounds for the running time. We illustrate the results on the specific problem of integer factorization, which is of central interest for deciphering messages encrypted with the RSA cryptosystem.Comment: 23 pages, 8 figure

Climate Services to Support Disaster Risk Reduction and Climate Change Adaptation in Urban Areas: The CLARITY Project and the Napoli Case Study

Climate services are emerging worldwide as an essential tool to bridge the advancement in climate science and meteo/earth observations with a variety of operational fields in the domains of Disaster Risk Reduction (DRR) and Climate Change Adaptation (CCA). It is multidisciplinary study area with promising applications in the field of urban microclimate simulations, supporting climate-resilient redevelopment actions at both the city and neighborhood levels. The CLARITY CSIS (Climate Services Information System, available at https://csis.myclimateservice.eu/), developed within the H2020 CLARITY project, is an innovative hazard/impact modeling tool that takes into account short- to long-term climate change scenarios and urban microclimate variability. Disaster risks associated with climate change, such as heat waves and floods, are concentrated in limited periods of the year and therefore not adequately represented by annually averaged values. To this aim, new datasets have been extracted from Regional Climate Models to estimate the frequency of extreme temperatures and precipitation events until 2100, and a novel modeling methodology has been developed to capture the effect on the urban microclimate due to specific built environment features. The wide amount of data generated by satellite earth observations and made available at pan-European level through the Copernicus datasets (e.g., Urban Atlas, European Settlement Map, etc.) has been processed through specific algorithms and GIS spatial analysis tools to extract detailed information related to key parameters linked to urban morphology and surface types. In addition to the “screening service” available at the pan-European level through the CLARITY CSIS, an “expert service” workflow allows increasing the resolution of hazard and impact simulations at 250 m, by exploiting detailed land use datasets provided by local end-users and assessing the DRR/CCA potential of city-wide adaptation plans, as well as of specific district redevelopment projects. This paper will present the features of CLARITY CSIS and the results of Expert Services implemented for the City of Naples, focusing on the methods adopted to implement hazard/impact assessments and how information from climate services is tailored to support the integration of different DRR/CCA strategies within urban plans and projects