Two-walker discrete-time quantum walks on the line with percolation

One goal in the quantum-walk research is the exploitation of the intrinsic quantum nature of multiple walkers, in order to achieve the full computational power of the model. Here we study the behaviour of two non-interacting particles performing a quantum walk on the line when the possibility of lattice imperfections, in the form of missing links, is considered. We investigate two regimes, statical and dynamical percolation, that correspond to different time scales for the imperfections evolution with respect to the quantum-walk one. By studying the qualitative behaviour of three two-particle quantities for different probabilities of having missing bonds, we argue that the chosen symmetry under particle-exchange of the input state strongly affects the output of the walk, even in noisy and highly non-ideal regimes. We provide evidence against the possibility of gathering information about the walkers indistinguishability from the observation of bunching phenomena in the output distribution, in all those situations that require a comparison between averaged quantities. Although the spread of the walk is not substantially changed by the addition of a second particle, we show that the presence of multiple walkers can be beneficial for a procedure to estimate the probability of having a broken link.Comment: 16 pages, 9 figure

Improving the understandability of the next edition of the International System of Units (SI) by focusing on its conceptual structure

The International System of Units (SI) is fundamental for the social, and not only the scientific, role of metrology, and as such its understandability is a crucial issue. According to the current draft of the new SI Brochure, the next edition of the SI will be significantly more complex in its conceptual structure than the previous ones. Identifying a strategy for effectively communicating its main contents is then a worthwhile endeavor, in order to increase the acceptance and thus the sustainability of the SI itself. Our proposal is to focus on the semantic structure of the definitions: this is instrumental to the awareness campaigns recommended by the General Conference on Weights and Measures to make the next edition of the SI understandable by a diverse readership without compromising scientific rigor.Comment: 10 pages, 1 table, accepted on Journal MEASUREMEN

Mathematical Model of HIV superinfection dynamics and R5 to X4 switch

During the HIV infection several quasispecies of the virus arise, which are able to use different coreceptors, in particular the CCR5 and CXCR4 coreceptors (R5 and X4 phenotypes, respectively). The switch in coreceptor usage has been correlated with a faster progression of the disease to the AIDS phase. As several pharmaceutical companies are starting large phase III trials for R5 and X4 drugs, models are needed to predict the co-evolutionary and competitive dynamics of virus strains. We present a model of HIV early infection which describes the dynamics of R5 quasispecies and a model of HIV late infection which describes the R5 to X4 switch. We report the following findings: after superinfection or coinfection, quasispecies dynamics has time scales of several months and becomes even slower at low number of CD4+ T cells. The curve of CD4+ T cells decreases, during AIDS late stage, and can be described taking into account the X4 related Tumor Necrosis Factor dynamics. Phylogenetic inference of chemokine receptors suggests that viral mutational pathway may generate R5 variants able to interact with chemokine receptors different from CXCR4. This may explain the massive signaling disruptions in the immune system observed during AIDS late stages and may have relevance for vaccination and therapy.Comment: 21 pages, 14 figure

CHANGES OF THE EU POLICIES IN HORTICULTURE

The EU policy in horticulture has switched its aim from price support to integration of farmers' income. Regulation 2200/96 established the new European Market Regulation (CMO) in horticulture. On this base the producers' organizations (PO) are no longer a political institution but a real economic organization with the objectives of planning and concentrating the production. At the same time, the UE has promulgated another plan (Decision n.2796 of 10/10/96 applying the objectives of the Reg. 2081/93), which is specific for Italian regions in "Objective 1" namely with low average income. This issue establishes the commercial macro organizations with the target of concentrating the supply of the producers' organizations in order to achieve countervailing power and economies of scale in services and trade. These new issues come out within a general framework of international agreements promoting cooperation and free trade areas (Mediterranean, Magreb, PECO,...). The impact on the European horticultural system will be tremendous in terms of production assessment and food chain organization and management.horticulture, European Union, market, policy, Agricultural and Food Policy, Q13,

Stochastic gravitational background from inflationary phase transitions

We consider true vacuum bubbles generated in a first order phase transition occurring during the slow rolling era of a two field inflation: it is known that gravitational waves are produced by the collision of such bubbles. We find that the epoch of the phase transition strongly affects the characteristic peak frequency of the gravitational waves, causing an observationally interesting redshift in addition to the post-inflationary expansion. In particular it is found that a phase transition occurring typically 10$\div$20 $e-$foldings before the reheating at $kT\simeq 10^{15}$ GeV may be detected by the next Ligo gravity waves interferometers. Moreover, for recently proposed models capable of generating the observed large scale voids as remnants of the primordial bubbles (for which the characteristic wave lengths are several tens of Mpc), it is found that the level of anisotropy of the cosmic microwave background provides a deep insight upon the physical parameters of the effective Lagrangian.Comment: 12 pages, 3 figures. Phys.Rev.D in pres

Future Cities and Regions. Simulation, Scenario and Visioning, Governance and Scales

This guide for tomorrow's urban practitioner systematically explains fourteen best practices across three continents; it explores questions of broad interest for designing and planning the future of cities and regions. Key questions addressed are: Is simulation useful to explore the effects of different design, policy and planning strategies? Which approach will help manage the uncertainties of metropolitan areas both today and tomorrow ? What are the strengths and weaknesses of the different simulation practices for city leadership, public and private partnership, and citizen involvement? The book reviews computer models and media, socio-political initiatives, professional practices which help communicating the future effects of different design, political and planning strategies with a wide range of aims: from information, through consultation, towards active participation. These world best practices are considered according to four leading issues for urban and regional development, respectively Simulation, Scenario and Visioning, Government and Governance, and Scale. The book examines the approaches adopted technically and procedurally. The selected knowledge and the innovative tools used in each case study are among the most advanced and up-to-date in the professional and research fields. This volume successfully illustrates these innovative practices and methodologies in a straightforward and accessible wa

Constants in Future Cities and Regions

The paper resumes some of the conversations the authors had in three years of research, based on the review of best participatory planning practices worldwide. The case projects are selected and discussed with the protagonists across four leading issues: Simulation, Scenario and Visioning, Government and Governance, and Scale. The case-oriented discussion is a peculiarity of the book , contributing to give shape to future cities or regions. The aim is to build a critical thinking on how urban planning, policy and design issues are faced differently or similarly throughout every cases studied. The book include the description of computer models and media, socio-political experiments and professional practices which help communicating the future effects of different design, policy and planning strategies and schemes with a wide range of aims: from information, through consultation, towards active participation. The cases have confirmed that simulation tools can impact on local government and can drive new forms of "glocal" governance, shaping and implementing future plans and projects at different scale and time span. The following paragraphs will point at some of the constant thoughts the authors had around the selection and editing of the book's case studied and related issue