Current quantization and fractal hierarchy in a driven repulsive lattice gas

Driven lattice gases are widely regarded as the paradigm of collective phenomena out of equilibrium. While such models are usually studied with nearest-neighbor interactions, many empirical driven systems are dominated by slowly decaying interactions such as dipole-dipole and Van der Waals forces. Motivated by this gap, we study the non-equilibrium stationary state of a driven lattice gas with slow-decayed repulsive interactions at zero temperature. By numerical and analytical calculations of the particle current as a function of the density and of the driving field, we identify (i) an abrupt breakdown transition between insulating and conducting states, (ii) current quantization into discrete phases where a finite current flows with infinite differential resistivity, and (iii) a fractal hierarchy of excitations, related to the Farey sequences of number theory. We argue that the origin of these effects is the competition between scales, which also causes the counterintuitive phenomenon that crystalline states can melt by increasing the density

Tactical urbanism experiences in building public spaces: lessons learned in Italy

Urban planning has changed its paradigm following the evolution of the development approach from unlimited growth to sustainable development (Daly 2014; OECD 2020). The need to save natural resources (particularly the soil), to fight climate change, to favor local economic development, have brought about a paradigm shift also in urban planning that has moved the focus of disciplinary interest from the indefinite expansion of urban suburbs to the regeneration of the existing city both in its physical spaces and in its society (Van der Zwet and Ferry 2019; EC 2020; Beer and Clower 2019; Medeiros and van der Zwet 2020). In urban regeneration processes, the degraded spaces and the residual voids of previous expansion cycles have become the privileged spaces for new projects (Magnaghi 2005). Social reasons for changes in urban planning have been added to the environmental ones, linked to the contemporary demographic dynamics of most Western nations experiencing a phase of demographic contraction. The shrinking cities phenomenon and its consequences have been explored in a large international literature (Oswalt and Rieniets 2006; Pallagst et al. 2009; Audirac and Alejandre 2010; Camarda et al. 2015). After reductions in mortality, fertility not only decreased but reached values lower than those of generational replacement (which corresponds to approximately two children per woman). The European continent, as a whole, has collapsed below this threshold since the second half of the 1970s. The current European Union figure is just over 1.5. The United States managed to remain close to the replacement value for longer, but in the last decade it has suffered a significant reduction (United Nations 2022). Naturally, demographic dynamics are very different for nations like China or India. Even more than in the past, growth rates between areas of the world and between generations have never been so divergent. Such processes of ecological and demographic transition have forced development models to change with obvious and decisive consequences also in urban planning. Urban regeneration of existing cities is the main objective of urban planning and the main tool of urban design. But how should urban regeneration processes be carried out? There are project tools that allow “planning by doing” as Campos Venuti (1978) elaborated in another historical context, anticipating and verifying the possible consequences of design choices and allowing the inhabitants to realize this directly by experimenting with the solutions without having to read difficult three-dimensional models or to be anxious about spending a lot of public money without being able to go back on the choices made. There have been multiple ways of defining possible answers to these questions which have taken on different names often indicating very similar interventions such as: “do-it-yourself” (DIY), “pop-up”, “guerilla”, and “tactical urbanism”. All these practices (many of them already discussed by Lydon 2011; Lydon and Garcia 2015; and Bishop and Williams 2012) were informal and temporary urban design governance actions, very often related to bottom-up processes of community empowerment (a panorama of these European informal urban design governance practices has been made by the Urban Maestro organization,1 summarized and discussed by Carmona et al. 2023), and used as urban regeneration catalysts (Oswalt et al. 2014). With the spread of these experiences throughout the world, institutions have also begun to realize that these types of interventions, especially if placed within broader urban regeneration strategies, might no longer be promoted only by inhabitants or autonomous groups of interests (often to counteract the inertia of institutions in tackling the degradation of some places), but also directly by the institutions themselves. In this new institutional context, tactical urbanism (TU) has come to be regarded as a regeneration tool capable of providing innovative answers to pressing problems in cities and urban areas

Tactical Urbanism in Italy: From Grassroots to Institutional Tool—Assessing Value of Public Space Experiments

none3The paper aims to evaluate the value that the experimentation of tactical urban planning activities can assume for the city, through the critical account of some practices in three Italian cities of large (Milan), medium-large (Bari), and medium size (Taranto), which in recent years, in some cases unknowingly, have experienced its effects, also forced by the thrust offered by the need to respond to the consequences of the pandemic. The authors reflect on how short-term interventions started by tactical urbanism movement are inspiring planning institutions to implement short-term place-making initiatives. The contribution moves within the context of new generation urban regeneration in which the transformation of existing spaces is a process of community reconstruction through the redevelopment of public spaces increasingly open to multiple and temporary uses. First through a process of rereading the state of the art of the project of public spaces in Italy and its transformation caused by the pandemic, then through a comparative look between the three case studies, conclusions are drawn on the urban value of the experiments conducted and, on their ability, to identify a new reference point for the sustainable urban regeneration of public spaces.openCariello Alessandro, Ferorelli Rossella, Rotondo, FrancescoCariello, Alessandro; Ferorelli, Rossella; Rotondo, Francesc

Statistical mechanics of transfer learning in fully-connected networks in the proportional limit

Transfer learning (TL) is a well-established machine learning technique to boost the generalization performance on a specific (target) task using information gained from a related (source) task, and it crucially depends on the ability of a network to learn useful features. Leveraging recent analytical progress in the proportional regime of deep learning theory (i.e. the limit where the size of the training set $P$ and the size of the hidden layers $N$ are taken to infinity keeping their ratio $\alpha = P/N$ finite), in this work we develop a novel single-instance Franz-Parisi formalism that yields an effective theory for TL in fully-connected neural networks. Unlike the (lazy-training) infinite-width limit, where TL is ineffective, we demonstrate that in the proportional limit TL occurs due to a renormalized source-target kernel that quantifies their relatedness and determines whether TL is beneficial for generalization

Observation of J/ψpJ/\psi p resonances consistent with pentaquark states in Λb0→J/ψK−p{\Lambda_b^0\to J/\psi K^-p} decays

Observations of exotic structures in the $J/\psi p$ channel, that we refer to as pentaquark-charmonium states, in $\Lambda_b^0\to J/\psi K^- p$ decays are presented. The data sample corresponds to an integrated luminosity of 3/fb acquired with the LHCb detector from 7 and 8 TeV pp collisions. An amplitude analysis is performed on the three-body final-state that reproduces the two-body mass and angular distributions. To obtain a satisfactory fit of the structures seen in the $J/\psi p$ mass spectrum, it is necessary to include two Breit-Wigner amplitudes that each describe a resonant state. The significance of each of these resonances is more than 9 standard deviations. One has a mass of $4380\pm 8\pm 29$ MeV and a width of $205\pm 18\pm 86$ MeV, while the second is narrower, with a mass of $4449.8\pm 1.7\pm 2.5$ MeV and a width of $39\pm 5\pm 19$ MeV. The preferred $J^P$ assignments are of opposite parity, with one state having spin 3/2 and the other 5/2.Comment: 48 pages, 18 figures including the supplementary material, v2 after referee's comments, now 19 figure

Optimism and Its Impact on Mental and Physical Well-Being

Many studies have been carried out about the effectiveness of optimism as a psychological phenomenon, leading to various theoretical formulations of the same concept, conceptualized as “disposition”, “attributional style”, “cognitive bias”, or “shared illusion”. This overview is an attempt to explore the “optimism” concept and its relations with mental health, physical health, coping, quality of life and adaptation of purpose, health lifestyle and risk perception

Measurement of ISR-FSR interference in the processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi- gamma

Charge asymmetry in processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi- gamma is measured using 232 fb-1 of data collected with the BABAR detector at center-of-mass energies near 10.58 GeV. An observable is introduced and shown to be very robust against detector asymmetries while keeping a large sensitivity to the physical charge asymmetry that results from the interference between initial and final state radiation. The asymmetry is determined as afunction of the invariant mass of the final-state tracks from production threshold to a few GeV/c2. It is compared to the expectation from QED for e+ e- --> mu+ mu- gamma and from theoretical models for e+ e- --> pi+ pi- gamma. A clear interference pattern is observed in e+ e- --> pi+ pi- gamma, particularly in the vicinity of the f_2(1270) resonance. The inferred rate of lowest order FSR production is consistent with the QED expectation for e+ e- --> mu+ mu- gamma, and is negligibly small for e+ e- --> pi+ pi- gamma.Comment: 32 pages,29 figures, to be submitted to Phys. Rev.

Tracker Operation and Performance at the Magnet Test and Cosmic Challenge

During summer 2006 a fraction of the CMS silicon strip tracker was operated in a comprehensive slice test called the Magnet Test and Cosmic Challenge (MTCC). At the MTCC, cosmic rays detected in the muon chambers were used to trigger the readout of all CMS sub-detectors in the general data acquisition system and in the presence of the 4 T magnetic field produced by the CMS superconducting solenoid. This document describes the operation of the Tracker hardware and software prior, during and after data taking. The performance of the detector as resulting from the MTCC data analysis is also presented

Neurological vertigo in the emergency room in pediatric and adult age: systematic literature review and proposal for a diagnostic algorithm

Neurological vertigo is a common symptom in children and adults presenting to the emergency department (ED) and its evaluation may be challenging, requiring often the intervention of different medical specialties. When vertigo is associated with other specific symptoms or signs, a differential diagnosis may be easier. Conversely, if the patient exhibits isolated vertigo, the diagnostic approach becomes complex and only through a detailed history, a complete physical examination and specific tests the clinician can reach the correct diagnosis. Approach to vertigo in ED is considerably different in children and adults due to the differences in incidence and prevalence of the various causes. The aim of this systematic review is to describe the etiopathologies of neurological vertigo in childhood and adulthood, highlighting the characteristics and the investigations that may lead clinicians to a proper diagnosis. Finally, this review aims to develop an algorithm that could represent a valid diagnostic support for emergency physicians in approaching patients with isolated vertigo, both in pediatric and adult age

Measurement of the forward Z boson production cross-section in pp collisions at s=13\sqrt{s} = 13 TeV

A measurement of the production cross-section of Z bosons in pp collisions at $\sqrt{s} = 13$ TeV is presented using dimuon and dielectron final states in LHCb data. The cross-section is measured for leptons with pseudorapidities in the range $2.0 \eta 4.5$, transverse momenta $p_\text{T} 20$ GeV and dilepton invariant mass in the range $60 m(\ell\ell) 120$ GeV. The integrated cross-section from averaging the two final states is \begin{equation*}\sigma_{\text{Z}}^{\ell\ell} = 194.3 \pm 0.9 \pm 3.3 \pm 7.6\text{ pb,}\end{equation*} where the first uncertainty is statistical, the second is due to systematic effects, and the third is due to the luminosity determination. In addition, differential cross-sections are measured as functions of the Z boson rapidity, transverse momentum and the angular variable $\phi^*_\eta$