Stochastic approach to diffusion inside the chaotic layer of a resonance

We model chaotic diffusion, in a symplectic 4D map by using the result of a theorem that was developed for stochastically perturbed integrable Hamiltonian systems. We explicitly consider a map defined by a free rotator (FR) coupled to a standard map (SM). We focus in the diffusion process in the action, $I$, of the FR, obtaining a semi--numerical method to compute the diffusion coefficient. We study two cases corresponding to a thick and a thin chaotic layer in the SM phase space and we discuss a related conjecture stated in the past. In the first case the numerically computed probability density function for the action $I$ is well interpolated by the solution of a Fokker-Planck (F-P) equation, whereas it presents a non--constant time delay respect to the concomitant F-P solution in the second case suggesting the presence of an anomalous diffusion time scale. The explicit calculation of a diffusion coefficient for a 4D symplectic map can be useful to understand the slow diffusion observed in Celestial Mechanics and Accelerator Physics.Comment: This is the author's version of a work that was submitted to Physical Review E (http://pre.aps.org

IS LOCAL A MATTER OF FOOD MILES OR FOOD TRADITIONS?

In the last decade, the local food movement has achieved a growing popularity in the Italian food system. Nevertheless, the Italian food market still lacks a shared definition and labels indicating the local origin of the food products. In this study, we explore the meaning of \u201clocal food\u201d in the Italian market using a qualitative approach. Results from twenty-three individual semi-structured interviews show that the meaning of \u201clocal\u201d should be explained more in terms of connection between a community traditions and a geographical area than in terms of food miles

RECENT DEVELOPMENTS OF THE EU FARMLAND MARKETS: NATIONAL VARIABLES AND COMPARATIVE EFFECTS OF THE CAP REFORM IN SELECTED COUNTRIES

The present paper consists of two main parts. The first one gives a picture of the more recent development of the farmland market in selected EC countries since 1985/86. Two main indicators are used to make relatively comparable the observed trends concerning: i) land mobility, ii) farmland values. The second one tries to evaluate the effects of the CAP reform and the influence of national variables overtime, taking into account the following indicators: i) mobility (on land transfers; on tenancy), ii) income (for agricultural or forest use), iii) farmland values (in the plain; in the hill/mountain areas). Considerations on land market complexity and segmentation are finally included, with justification on the empirical approach adopted in the paper.

Analysis of adiabatic trapping phenomena for quasi-integrable area-preserving maps in the presence of time-dependent exciters

In this paper, new results concerning the phenomenon of adiabatic trapping into resonance for a class of quasi-integrable maps with a time-dependent exciter are presented and discussed in detail. The applicability of the results about trapping efficiency for Hamiltonian systems to the maps considered is proven by using perturbation theory. This allows determining explicit scaling laws for the trapping properties. These findings represent a generalization of previous results obtained for the case of quasi-integrable maps with parametric modulation as well as an extension of the work by Neishtadt \textit{et al.} on a restricted class of quasi-integrable systems with time-dependent exciters

Hamiltonian theory of the crossing of the 2Qx−2Qy=0 nonlinear coupling resonance

In a recent paper, the adiabatic theory of Hamiltonian systems was successfully applied to study the crossing of the linear coupling resonance, $Q_x-Q_y=0$. A detailed explanation of the well-known phenomena that occur during the resonance-crossing process, such as emittance exchange and its dependence on the adiabaticity of the process was obtained. In this paper, we consider the crossing of the resonance of nonlinear coupling $2 Q_x -2 Q_y = 0$ using the same theoretical framework. We perform the analysis using a Hamiltonian model in which the nonlinear coupling resonance is excited and the corresponding dynamics is studied in detail, in particular looking at the phase-space topology and its evolution, in view of characterizing the emittance exchange phenomena. The theoretical results are then tested using a symplectic map. Thanks to this approach, scaling laws of general interest for applications are derived

Consumers’ valuation for lab produced meat: an investigation of naming effects

“In-vitro” meat (IVM) technology could be seen as a solution that could overcome some of the concerns linked to conventional meat production, such as the expected demand increase, pressure on crop outputs, large greenhouse emission, high land, energy and water usage as well as consumers’ concerns related to animal welfare. One of the main drawback of IVM is that consumers’ might be reluctant to consume meat from this technology due to the perceived revulsion, lack of naturalness, taste, uncertainty about environmental benefits, and safety concerns. In this research, we aim to investigate consumers’ perception and willingness to pay (WTP) for IVM chicken by testing whether the use of different names for the IVM technology (i.e. “cultured”, “lab-grown” and “artificial”) will lead to different consumers’ preferences and WTP values. We conducted an online choice experiment (CE) in the United States with 625 participants to elicit consumers’ WTP for IVM fresh skinless boneless chicken breast products. To test naming effects, we used a between-subjects approach by randomly assigning respondents to three treatments. The treatments differed only on the name used to describe IVM technology (i.e. “cultured”, “lab-grown” and “artificial”). Results from Random Parameters Logit (RPL) models in WTP space shows that on average consumers prefer fresh skinless boneless chicken breast products produced with conventional meat technology with information about antibiotics free. Consumers tend to highly reject the IVM technology, with strong differences across the names. The term “cultured” is less disliked than the terms “artificial” and “lab-grown”. Finally, implications and suggestions for policy makers and food operators are discussed along with future research avenues

Probing the diffusive behaviour of beam-halo dynamics in circular accelerators

Circular particle accelerators at the energy frontier are based on superconducting magnets that are extremely sensitive to beam losses as these might induce quenches, i.e. transitions to the normal-conducting state. Furthermore, the energy stored in the circulating beam is so large that hardware integrity is put in serious danger, and machine protection becomes essential for reaching the nominal accelerator performance. In this challenging context, the beam halo becomes a potential source of performance limitations and its dynamics needs to be understood in detail to assess whether it could be an issue for the accelerator. In this paper, we discuss in detail a recent framework, based on a diffusive approach, to model beam-halo dynamics. The functional form of the optimal estimate of the perturbative series, as given by Nekhoroshev’s theorem, is used to provide the functional form of the action diffusion coefficient. The goal is to propose an effective model for the beam-halo dynamics and to devise an efficient experimental procedure to obtain an accurate measurement of the diffusion coefficient

Using FADN Data to Estimate CO2 Abatement Costs from Italian Arable Crops

The assessment of economic and environmental sustainability of agricultural systems represents a critical issue, which has been addressed in this work with a multi-objective programming model to explore the abatement costs (AC) of CO2 for a set of representative contexts of Italian arable land agriculture. The study was based on the FADN-compliant Italian database RICA and estimates the abatement costs of CO2 emissions in a short time horizon, using linear multi-objective programming and compromise programming. RICA data were used to quantify technical parameters of the model, adopting an innovative concept of a cropping scheme to simulate land-use adaptation. The study shows a quite diversified situation regarding income and emission levels per hectare across the Italian region and farm classes. A reduction of CO2 emissions higher than 5 kg/ha at an AC lower than 1 EUR/kg is affordable only in seven regions, among which Abruzzo, Lombardy, and Puglia show the highest potential. Comparing the estimated abatement costs for CO2 emissions with the corresponding European Trade System prices highlights a difference of 1 order of magnitude, proving that emission reductions for Italian arable crops still require research and innovation to lower adaptation costs

3D solutions of the Poisson-Vlasov equations for a charged plasma and particle-core model in a line of FODO cells

We consider a charged plasma of positive ions in a periodic focusing channel of quadrupolar magnets in the presence of RF cavities. The ions are bunched into charged triaxial ellipsoids and their description requires the solution of a fully 3D Poisson-Vlasov equation. We also analyze the trajectories of test particles in the exterior of the ion bunches in order to estimate their diffusion rate. This rate is relevant for a high intensity linac (TRASCO project). A numerical PIC scheme to integrate the Poisson-Vlasov equations in a periodic focusing system in 2 and 3 space dimensions is presented. The scheme consists of a single particle symplectic integrator and a Poisson solver based on FFT plus tri-diagonal matrix inversion. In the 2D version arbitrary boundary conditions can be chosen. Since no analytical self-consistent 3D solution is known, we chose an initial Neuffer-KV distribution in phase space, whose electric field is close to the one generated by a uniformly filled ellipsoid. For a matched (periodic) beam the orbits of test particles moving in the field of an ellipsoidal bunch, whose semi-axis satisfy the envelope equations, is similar to the orbits generated by the self-consistent charge distribition obtained from the PIC simulation, even though it relaxes to a Fermi-Dirac-like distribution. After a transient the RMS radii and emittances have small amplitude oscillations. The PIC simulations for a mismatched (quasiperiodic) beam are no longer comparable with the ellipsoidal bunch model even though the qualitative behavior is the same, namely a stronger diffusion due to the increase of resonances