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Iorio L.,R.A.U.M. | Ruggiero M.L.,University Telematica Internazionale Uninettuno | Ruggiero M.L.,Polytechnic University of Turin
International Journal of Modern Physics A | Year: 2010

We focus on HořavaLifshitz (HL) theory of gravity, and, in particular, on the Kehagias and Sfetsos's solution that is the analog of Schwarzschild black hole of General Relativity. In the weak-field and slow-motion approximation, we analytically work out the secular precession of the longitude of the pericentre ̄ω of a test particle induced by this solution. Its analytical form is different from that of the general relativistic Einstein's pericentre precession. Then, we compare it to the latest determinations of the corrections Δ ̄ω̇ to the standard Newtonian/Einsteinian planetary perihelion precessions recently estimated by E. V. Pitjeva with the EPM2008 ephemerides. It turns out that the planets of the solar system, taken singularly one at a time, allow one to put lower bounds on the adimensional HL parameter ψ0 of the order of 10-12 (Mercury)-10-24 (Pluto). They are not able to account for the Pioneer anomalous acceleration for r > 20 AU. © 2010 World Scientific Publishing Company.

Neff P.,University of Duisburg - Essen | Ghiba I.-D.,University of Duisburg - Essen | Madeo A.,University Claude Bernard Lyon 1 | Placidi L.,University Telematica Internazionale Uninettuno | Rosi G.,CNRS Multiscale Modelling and Simulation Laboratory
Continuum Mechanics and Thermodynamics | Year: 2014

We formulate a relaxed linear elastic micromorphic continuum model with symmetric Cauchy force stresses and curvature contribution depending only on the micro-dislocation tensor. Our relaxed model is still able to fully describe rotation of the microstructure and to predict nonpolar size effects. It is intended for the homogenized description of highly heterogeneous, but nonpolar materials with microstructure liable to slip and fracture. In contrast to classical linear micromorphic models, our free energy is not uniformly pointwise positive definite in the control of the independent constitutive variables. The new relaxed micromorphic model supports well-posedness results for the dynamic and static case. There, decisive use is made of new coercive inequalities recently proved by Neff, Pauly and Witsch and by Bauer, Neff, Pauly and Starke. The new relaxed micromorphic formulation can be related to dislocation dynamics, gradient plasticity and seismic processes of earthquakes. It unifies and simplifies the understanding of the linear micromorphic models. © 2013 Springer-Verlag Berlin Heidelberg.

Ruggiero M.L.,University Telematica Internazionale Uninettuno | Ruggiero M.L.,Polytechnic University of Turin | Iorio L.,National Institute of Nuclear Physics, Italy
General Relativity and Gravitation | Year: 2010

We study the effects of a time-varying gravitomagnetic field on the motion of test particles. Starting from recent results, we consider the gravitomagnetic field of a source whose spin angular momentum has a linearly time-varying magnitude. The acceleration due to such a time-varying gravitomagnetic field is considered as a perturbation of the Newtonian motion, and we explicitly evaluate the effects of this perturbation on the Keplerian elements of a closed orbit. The theoretical predictions are compared with actual astronomical and astrophysical scenarios, both in the solar system and in binary pulsars systems, in order to evaluate the impact of these effects on real systems. © 2010 Springer Science+Business Media, LLC.

Cacciapuoti C.,University of Insubria | Finco D.,University Telematica Internazionale Uninettuno | Noja D.,University of Milan Bicocca
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2015

In this paper we give the complete classification of solitons for a cubic nonlinear Schrödinger equation on the simplest network with a nontrivial topology: the tadpole graph, i.e., a ring with a half line attached to it and free boundary conditions at the junction. This is a step toward the modelization of condensate propagation and confinement in quasi-one-dimensional traps. The model, although simple, exhibits a surprisingly rich behavior and in particular we show that it admits: (i) a denumerable family of continuous branches of embedded solitons vanishing on the half line and bifurcating from linear eigenstates and threshold resonances of the system; (ii) a continuous branch of edge solitons bifurcating from the previous families at the threshold of the continuous spectrum with a pitchfork bifurcation; and (iii) a finite family of continuous branches of solitons without linear analog. All the solutions are explicitly constructed in terms of elliptic Jacobian functions. Moreover we show that families of nonlinear bound states of the above kind continue to exist in the presence of a uniform magnetic field orthogonal to the plane of the ring when a well definite flux quantization condition holds true. In this sense the magnetic field acts as a control parameter. Finally we highlight the role of resonances in the linearization as a signature of the occurrence of bifurcations of solitons from the continuous spectrum. © 2015 American Physical Society.

Assante D.,University Telematica Internazionale Uninettuno | Verolino L.,University of Naples Federico II
Progress In Electromagnetics Research M | Year: 2012

We discuss the electromagnetic interaction between a traveling charge particle and a perfectly conducting strip of a negligible thickness. The particle travels at a constant velocity along a straight line parallel to the axis of symmetry of the strip. The efficiency of the proposed solution is proved by evaluating the longitudinal coupling impedance in a wide range of parameters.

Adami R.,University of Milan Bicocca | Adami R.,CNR Institute for Applied Mathematics and Information Technologies | Cacciapuoti C.,Institute For Angewandte Mathematik | Finco D.,University Telematica Internazionale Uninettuno | And 2 more authors.
Journal of Physics A: Mathematical and Theoretical | Year: 2012

We provide information on a non-trivial structure of phase space of the cubic nonlinear Schrödinger (NLS) on a three-edge star graph. We prove that, in contrast to the case of the standard NLS on the line, the energy associated with the cubic focusing Schrödinger equation on the three-edge star graph with a free (Kirchhoff) vertex does not attain a minimum value on any sphere of constant L 2-norm. We moreover show that the only stationary state with prescribed L 2-norm is indeed a saddle point. © 2012 IOP Publishing Ltd.

Bonifaci V.,University Telematica Internazionale Uninettuno | Salek M.,University of Southern California | Schafer G.,VU University Amsterdam
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2011

An effective means to reduce the inefficiency of Nash flows in non-atomic network routing games is to impose tolls on the arcs of the network. It is a well-known fact that marginal cost tolls induce a Nash flow that corresponds to a minimum cost flow. However, despite their effectiveness, marginal cost tolls suffer from two major drawbacks, namely (i) that potentially every arc of the network is tolled, and (ii) that the imposed tolls can be arbitrarily large. In this paper, we study the restricted network toll problem in which tolls can be imposed on the arcs of the network but are restricted to not exceed a predefined threshold for every arc. We show that optimal restricted tolls can be computed efficiently for parallel-arc networks and affine latency functions. This generalizes a previous work on taxing subnetworks to arbitrary restrictions. Our algorithm is quite simple, but relies on solving several convex programs. The key to our approach is a characterization of the flows that are inducible by restricted tolls for single-commodity networks. We also derive bounds on the efficiency of restricted tolls for multi-commodity networks and polynomial latency functions. These bounds are tight even for parallel-arc networks. Our bounds show that restricted tolls can significantly reduce the price of anarchy if the restrictions imposed on arcs with high-degree polynomials are not too severe. Our proof is constructive. We define tolls respecting the given thresholds and show that these tolls lead to a reduced price of anarchy by using a (λ,μ)-smoothness approach. © 2011 Springer-Verlag.

Adami R.,University of Milan Bicocca | Cacciapuoti C.,Institute For Angewandte Mathematik | Finco D.,University Telematica Internazionale Uninettuno | Noja D.,University of Milan Bicocca
Reviews in Mathematical Physics | Year: 2011

We define the Schrödinger equation with focusing, cubic nonlinearity on one-vertex graphs. We prove global well-posedness in the energy domain and conservation laws for some self-adjoint boundary conditions at the vertex, i.e. Kirchhoff boundary condition and the so-called δ and δ′ boundary conditions. Moreover, in the same setting, we study the collision of a fast solitary wave with the vertex and we show that it splits in reflected and transmitted components. The outgoing waves preserve a soliton character over a time which depends on the logarithm of the velocity of the ingoing solitary wave. Over the same timescale, the reflection and transmission coefficients of the outgoing waves coincide with the corresponding coefficients of the linear problem. In the analysis of the problem, we follow ideas borrowed from the seminal paper [17] about scattering of fast solitons by a delta interaction on the line, by Holmer, Marzuola and Zworski. The present paper represents an extension of their work to the case of graphs and, as a byproduct, it shows how to extend the analysis of soliton scattering by other point interactions on the line, interpreted as a degenerate graph. © 2011 World Scientific Publishing Company.

Mazali T.,University Telematica Internazionale Uninettuno
Leonardo | Year: 2011

The information and communication technology system is constantly creating new scenarios, but a tendency in them can still be recognized: the blurring of the limits between consumers and producers and the passage from interactivity to participation (user generated contents, web 2.0, social networks). In this emerging cultural context, constantly redefined and remediated by individual and personalized forms of elaboration, it is important to understand the way in which every single person or group leads his/her own way towards reappropriation of the technological realm. The author aims to explore potential and real capacities of these new technologies to generate a new public sphere by analyzing an exemplary case study: the moblog communities in the megaphone.net project. © 2011 ISAST.

Nardinocchi P.,University of Rome La Sapienza | Pezzulla M.,University of Rome La Sapienza | Placidi L.,University Telematica Internazionale Uninettuno
Journal of Intelligent Material Systems and Structures | Year: 2011

The modeling of the complex response of the IPMC-like body to electrical and mechanical stimuli is set within the context of the 3-D theory of linear elasticity. A field of chemically induced distortions is included in the model; these mechanical distortions and the derivation of the final PDE equations of the multiphysics problem are thermodynamically consistent. Some results of the numerical experiments are revisited through an original analysis of the stress distribution along the IPMC-like body. © The Author(s) 2011.

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