Rotating Globular Clusters

Internal rotation is considered to play a major role in the dynamics of some globular clusters. However, in only few cases it has been studied by quantitative application of realistic and physically justified global models. Here we present a dynamical analysis of the photometry and three-dimensional kinematics of omega Cen, 47 Tuc, and M15, by means of a recently introduced family of self-consistent axisymmetric rotating models. The three clusters, characterized by different relaxation conditions, show evidence of differential rotation and deviations from sphericity. The combination of line-of-sight velocities and proper motions allows us to determine their internal dynamics, predict their morphology, and estimate their dynamical distance. The well-relaxed cluster 47 Tuc is very well interpreted by our model; internal rotation is found to explain the observed morphology. For M15, we provide a global model in good agreement with the data, including the central behavior of the rotation profile and the shape of the ellipticity profile. For the partially relaxed cluster omega Cen, the selected model reproduces the complex three-dimensional kinematics; in particular the observed anisotropy profile, characterized by a transition from isotropy, to weakly-radial anisotropy, and then to tangential anisotropy in the outer parts. The discrepancy found for the steep central gradient in the observed line-of-sight velocity dispersion profile and for the ellipticity profile is ascribed to the condition of only partial relaxation of this cluster and the interplay between rotation and radial anisotropy.Comment: 19 pages, 14 figures, accepted for publication in the Astrophysical Journa

A nonhomogeneous boundary value problem in mass transfer theory

We prove a uniqueness result of solutions for a system of PDEs of Monge-Kantorovich type arising in problems of mass transfer theory. The results are obtained under very mild regularity assumptions both on the reference set $\Omega\subset\mathbf{R}^n$, and on the (possibly asymmetric) norm defined in $\Omega$. In the special case when $\Omega$ is endowed with the Euclidean metric, our results provide a complete description of the stationary solutions to the tray table problem in granular matter theory.Comment: 22 pages, 2 figure

The unusual 2006 dwarf nova outburst of GK Perseii

The 2006 outburst of GK Perseii differed significantly at optical and ultraviolet wavelengths from typical outbursts of this object. We present multi-wavelength (X-ray, UV and optical) Swift and AAVSO data, giving unprecedented broad-band coverage of the outburst, allowing us to follow the evolution of the longer-than-normal 2006 outburst across these wavelengths. In the optical and UV we see a triple-peaked morphology with maximum brightness ~1.5 magnitudes lower than in previous years. In contrast, the peak hard X-ray flux is the same as in previous outbursts. We resolve this dichotomy by demonstrating that the hard X-ray flux only accounts for a small fraction of the total energy liberated during accretion, and interpret the optical/UV outburst profile as arising from a series of heating and cooling waves traversing the disc, caused by its variable density profile.Comment: 9 pages, 7 figures, accepted for publication in MNRA

Nonlinear hyperbolic systems: Non-degenerate flux, inner speed variation, and graph solutions

We study the Cauchy problem for general, nonlinear, strictly hyperbolic systems of partial differential equations in one space variable. First, we re-visit the construction of the solution to the Riemann problem and introduce the notion of a nondegenerate (ND) system. This is the optimal condition guaranteeing, as we show it, that the Riemann problem can be solved with finitely many waves, only; we establish that the ND condition is generic in the sense of Baire (for the Whitney topology), so that any system can be approached by a ND system. Second, we introduce the concept of inner speed variation and we derive new interaction estimates on wave speeds. Third, we design a wave front tracking scheme and establish its strong convergence to the entropy solution of the Cauchy problem; this provides a new existence proof as well as an approximation algorithm. As an application, we investigate the time-regularity of the graph solutions $(X,U)$ introduced by the second author, and propose a geometric version of our scheme; in turn, the spatial component $X$ of a graph solution can be chosen to be continuous in both time and space, while its component $U$ is continuous in space and has bounded variation in time.Comment: 74 page

Road Infrastructure Safety Management. Proactive Safety Tools to Evaluate Potential Conditions of Risk

The identification of highly critical sections in a road network is possible by examining the network operation, with the goal of determining the risk factors and observe the critical issues, in order to better plan possible improvements. Therefore, this study proposes a method to evaluate the coherence of existing road layouts, through the analysis of the geometric characteristics, theoretical speeds and drivers operating speeds, under different environmental and flow conditions. The analysis focuses on the road network managed by ANAS SpA in the Veneto Region, for which the reconstruction of the road axes geometry, the curvature graph and the theoretical design speed profile have been obtained, according to the indications of the Italian Ministerial Decree 05/11/2001. The theoretical design speed profile has then been compared with the information relating to the road users' mobility, in terms of the 85th percentile speeds, obtained from the extraction and analysis of the Floating Car Data (FCD). The data were processed by reconstructing the continuous profile of operating speeds with a specific regression function known as "smoothing cubic spline". The comparison with the theoretical design speeds allows to observe whether the users assume a behavior close to or distant from what is expected, based on the technical and geometrical characteristics of the road layout. The proposed methodology can contribute to the implementation of a proactive road safety check, aimed at recognizing and assessing the potential risk conditions for road traffic, with particular attention to the point of view of the road user

Auto-oscillation threshold and line narrowing in MgO-based spin-torque oscillators

We present an experimental study of the power spectrum of current-driven magnetization oscillations in MgO tunnel junctions under low bias. We find the existence of narrow spectral lines, down to 8 MHz in width at a frequency of 10.7 GHz, for small applied fields with clear evidence of an auto-oscillation threshold. Micromagnetics simulations indicate that the excited mode corresponds to an edge mode of the synthetic antiferromagnet

SBV regularity for Hamilton-Jacobi equations in Rn\mathbb R^n

In this paper we study the regularity of viscosity solutions to the following Hamilton-Jacobi equations $$\partial_t u + H(D_{x} u)=0 \qquad \textrm{in} \Omega\subset \mathbb R\times \mathbb R^{n} .$$ In particular, under the assumption that the Hamiltonian $H\in C^2(\mathbb R^n)$ is uniformly convex, we prove that $D_{x}u$ and $\partial_t u$ belong to the class $SBV_{loc}(\Omega)$.Comment: 15 page

Trace-Element Distribution on Sulfide Mineralization in Trento Province, NE Italy

Sulfide mineralization in the province of Trento (northeastern Italy) includes various mineral assemblages that are often silver-rich and have been exploited in different phases from the Middle Ages until the 20th century. This study investigates mineralized rocks from three historically important sites (Calisio mount, Erdemolo lake, and the locality of Cinque Valli), providing new analytical data (Inductively Coupled Plasma-Mass Spectrometry on bulk rocks, and Scanning Electron Microscopy on thin sections) that demonstrate that parageneses do not only include galena, chalcopyrite, and sphalerite but also accessory minerals, such as tetrahedrite, tennantite, acanthite, and sulfosalts (matildite/polybasite). This explains the high content of As (up to 278 ppm), Bi (up to 176 ppm), and Sb (up to 691 ppm) that are associated with Pb–Cu–Zn mineralization. Notably, trace-element ratios indicate that, although closely associated from a geographical point of view, the studied sites are not genetically related and have to be referred to in distinct mineralization events, possibly induced by three diverse magmatic and hydrothermal phases that occurred in the Variscan post-orogenic setting. Besides geological and petrogenetic reconstruction, the new data outline potential geochemical risks, as they reveal a high concentration of elements characterized by marked toxicity that can be transferred into the local soil and water. Therefore, future studies should be devoted to better investigating the metal distribution in the surroundings of ancient mining sites and their geochemical behavior during the weathering processes

Quantitative FRAP by Means of Diffusion through 3D Polyelectrolyte Shells Using Confocal and Two-photon Excitation Approaches.

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