89 research outputs found
Care and Critical Action
No full textThis issue proposes care as a framework for critical action to critique capitalist modes of spatial production. We put forward perspectives on urban care, institutions of care, and care as agency, to argue that care as critical action refers to individual and collective mobilization for the radical changes society needs today. Regressive forms of individualism have undermined the social imagination and eroded civic institutions. Care for "the other," for individual and collective life, for the planet, and for the city must be brought to the forefront of our relations of thought.
This issue includes 11 papers, an afterword, and a visual essay by Patrizio Martinelli.
1 Cameron McEwan, Nadia Bertolino & Cristina Mattiucci, Editorial
2 Lorens Holm, My neighbour, the subject of civilisation
3 Nathanael Nelson, Deconstructing Hospitality. Postcolonial Care in the Built Environment
4 Andrew Copolov, The urban staffroom. Imagining infrastructures of care and solidarity in Melbourne
5 Ceara O’Leary, Community Hubs as Networks of Care
6 Jiayi Jin & Yuxin Wu, Careful Careless. A System to Restore Ecological Systems in Cities
7 Lee Ivett & Ecaterina Stefanescu, To Make is to Care
8 Jonathan Orlek, Claire McAndrew, Cristina Cerulli, Mara Ferreri, Marianna Cavada & Eleanor Ratcliffe, For a relational understanding of care in critical urban action
9 Sofia Rivera, The caregivers’ strike: a tale of violence and care in the entrails of San Salvador
10 Carolina Correia dos Santos & Iazana Guizzo, Paths of banana trees: passages of care between unequal worlds
11 Mathilde Redouté, Accurate commoning: between primitive and new enclosures
12 Huda Tayob, Archival Care
13 Cameron McEwan & Nadia Bertolino, Afterwor
Field localization and enhancement near the Dirac point of a finite defectless photonic crystal
No full textWe use a rigorous electromagnetic approach to show the existence of strongly localized modes in the stop band of a linear, two-dimensional, finite photonic crystal near its Dirac point. At normal incidence, the crystal exhibits a Dirac point with 100% transmission. At angles slightly off the normal, where the crystal is 100% reflective, instead of exponentially decaying fields as in a photonic stop band, the field becomes strongly localized and enhanced inside the crystal. We explain that this anomalous localization is due to guided mode resonances that are the foundation of the Dirac point itself and also shape its adjacent band gap. Besides shedding new light on the physical origin of Dirac points in finite photonic crystals, our results could have applications in many nonlinear light-matter interaction phenomena in which it is crucial to achieve a high degree of light localization. DOI: 10.1103/PhysRevB.87.08513
Ultraslow light pulses in a nonlinear metamaterial
No full textWe find the analytical expression for the threshold intensity necessary to launch ultraslow light pulses in a metamaterial with simultaneous cubic electric and magnetic nonlinearity. The roles played by the permittivity, the permeability, the electric cubic nonlinearity, the magnetic cubic nonlinearity and the pulse duration are clearly identified and discussed.G. D’Aguanno and N. Mattiucci acknowledge the National Research Council for financial support and thank Claudio Conti for helpful discussions.https://www.osapublishing.org/josab/abstract.cfm?uri=josab-25-8-123
Influence of losses on the superresolution performances of an impedance-matched negative-index material
No full textWe discuss by a Poynting vector analysis how the losses of a negative-index material (NIM) affect the resolution performances of a Veselago–Pendry lens, and we analyze those performances in the framework of the Abbe criterion. The limits of both high losses and low losses are explored. We find that the impedance-matched NIM is able to resolve 30% better than the limit imposed by the Abbe criterion even when the imaginary part of the refractive index (the material losses) exceeds the absolute value of the real part of the refractive index. The NIM is described by a lossy Drude model with equal permittivity and permeability. By increasing the damping parameter of the Drude model, we also explore the regime where both permittivity and permeability are positive and point out the conditions under which the metamaterial is still able to superresolve.G. D’Aguanno and N. Mattiucci thank the National Research Council for financial supporthttps://www.osapublishing.org/josab/abstract.cfm?uri=josab-25-2-23
Gap solitons in a nonlinear quadratic negative-index cavity
No full textWe predict the existence of gap solitons in a nonlinear, quadratic Fabry-Pérot negative index cavity. A peculiarity of a single negative index layer is that if magnetic and electric plasma frequencies are different it forms a photonic band structure similar to that of a multilayer stack composed of ordinary, positive index materials. This similarity also results in comparable field localization and enhancement properties that under appropriate conditions may be used to either dynamically shift the band edge, or for efficient energy conversion. We thus report that an intense, fundamental pump pulse is able to shift the band edge of a negative index cavity, and make it possible for a weak second harmonic pulse initially tuned inside the gap to be transmitted, giving rise to a gap soliton. The process is due to cascading, a well-known phenomenon that occurs far from phase matching conditions that limits energy conversion rates, it resembles a nonlinear third-order process, and causes pulse compression due to self-phase modulation. The symmetry of the equations of motion under the action of either an electric or a magnetic nonlinearity suggests that both nonlinear polarization and magnetization, or a combination of both, can lead to solitonlike pulses. More specifically, the antisymmetric localization properties of the electric and magnetic fields cause a nonlinear polarization to generate a dark soliton, while a nonlinear magnetization spawns a bright soliton. © 2007 The American Physical Society
Pulse propagation, dispersion, and energy in magnetic materials
No full textWe discuss pulse propagation effects in generic, electrically and magnetically dispersive media that may display large material discontinuities, such as a surface boundary. Using the known basic constitutive relations between the fields, and an explicit Taylor expansion to describe the dielectric susceptibility and magnetic permeability, we derive expressions for energy density and energy dissipation rates, and equations of motion for the coupled electric and magnetic fields. We then solve the equations of motion in the presence of a single interface, and find that in addition to the now-established negative refraction process an energy exchange occurs between the electric and magnetic fields as the pulse traverses the boundary
Radiation pressure of light pulses and conservation of linear momentum in dispersive media
No full textWe derive an expression for the Minkowski momentum under conditions of dispersive susceptibility and permeability, and compare it to the Abraham momentum in order to test the principle of conservation of linear momentum when matter is present. We investigate cases when an incident pulse interacts with a variety of structures, including thick substrates, resonant, free-standing, micron-sized multilayer stacks, and negative index materials. In general, we find that for media only a few wavelengths thick the Minkowski and Abraham momentum densities yield similar results. For more extended media, including substrates and Bragg mirrors embedded inside thick dielectric substrates, our calculations show dramatic differences between the Minkowski and Abraham momenta. Without exception, in all cases investigated the instantaneous Lorentz force exerted on the medium is consistent only with the rate of change of the Abraham momentum. As a practical example, we use our model to predict that electromagnetic momentum and energy buildup inside a multilayer stack can lead to widely tunable accelerations that may easily reach and exceed 10(10) m/s(2) for a mass of 10(-5) g. Our results suggest that the physics of the photonic band edge and other similar finite structures may be used as a testing ground for basic electromagnetic phenomena such as momentum transfer to macroscopic media
Dynamics of short pulses and phase matched second harmonic generation in negative index materials
No full textWe study pulsed second harmonic generation in metamaterials under conditions of significant absorption. Tuning the pump in the negative index range, a second harmonic signal is generated in the positive index region, such that the respective indices of refraction have the same magnitudes but opposite signs. This insures that a forward-propagating pump is exactly phase matched to the backward-propagating second harmonic signal. Using peak intensities of similar to 500 MW/cm(2), assuming chi((2))similar to 80pm/ V, we predict conversion efficiencies of 12% and 0.2% for attenuation lengths of 50 and 5 mu m, respectively. (c) 2006 Optical Society of America
The Role of the Phase Locking Phenomenon in the Second and Third Harmonics Cavity Localization
No full textFrontiers in Optics 2009, San Jose, California United States, 11–15 October 2009We theoretically and experimentally study how the phase-locking mechanism changes effective dispersion of the medium at the harmonic frequencies making them become localized inside a opaque cavity designed to be resonant for the fundamental field.We thank the U.S. Army European Research office for partial financial (support project W911NF). G.D. thanks the National Research Council for financial support. V.R., C.C., J.T. and R.V. acknowledge support from the Spanish government through Project No. FIS2008-06024-C03-02/FIS. We also thank Nadia Mattiucci and Mark J. Bloemer for helpful discussions and suggestions.https://www.osapublishing.org/abstract.cfm?uri=FiO-2009-FTuS
Migrazione e emergenza abitativa nel caso di Torino.
No full textAccording to the European Committee of Social Rights, the shortage of affordable housing in Europe—and in Italy in particular—constitutes a serious issue affecting an increasingly large share of the population. Barriers to access are even more pronounced for individuals with intersecting vulnerabilities, such as people with a migrant background. Although the right to housing for foreigners is guaranteed under Italian constitutional law as well as international and EU law, these groups experience greater difficulties, partly due to the lack of infrastructures that facilitate integration into housing pathways. One in two migrant households lives in overcrowded conditions (48.1percento, compared to 17.3percento among households composed solely of Italian nationals), highlighting the strong relationship between housing deprivation and migrant background (Istat 2022). Local territories often respond to this disparity with weak and insufficient emergency housing policies. This article proposes moving beyond such emergency driven approaches through an integrated analysis of the territorial housing access system, understood as a key indicator of integration trajectories. Launched in 2024, the Empower Housing study in the Turin metropolitan area assesses structural constraints and the socio economic variables that shape the transition from reception systems to autonomous housing pathways. Drawing on fieldwork, data collection and analysis, and structured dialogue with local stakeholders, the article examines innovative policies and practices for housing inclusion and outlines guidelines for co-design processes involving public authorities, the no profit sector, and private actors, while accounting for the specific needs of diverse migrant populations. Secondo il Comitato europeo per i diritti sociali, la carenza di alloggi a prezzi accessibili in Europa, e in Italia, è un problema grave che coinvolge una quota crescente della popolazione. Le barriere di accesso risultano ancora più marcate per soggetti con vulnerabilità intersezionali, come le persone con background migratorio. Pur essendo il diritto alla casa garantito dall’ordinamento italiano, internazionale e comunitario, tali gruppi sperimentano maggiori difficoltà anche per l’assenza di infrastrutture che facilitino l’integrazione abitativa. Una famiglia straniera su due vive in sovraffollamento (48,1percento, contro il 17,3percento delle famiglie italiane), evidenziando la forte relazione tra disagio abitativo e background migratorio (Istat 2022). A questa disparità i territori rispondono spesso con politiche emergenziali deboli e insufficienti. L’articolo propone di superare tali logiche attraverso un’analisi integrata del sistema territoriale di accesso all’alloggio, considerato indicatore cruciale dei percorsi di integrazione. Avviato nel 2024, lo studio Empower Housing, nel territorio torinese, valuta criticità strutturali e variabili socio economiche delle transizioni tra dispositivi di accoglienza e percorsi di autonomia. Basandosi su ricerca empirica e confronto con gli attori locali, l’articolo analizza politiche e pratiche di avanguardia per l’inclusione abitativa e propone linee guida per processi di coprogettazione tra pubblico, terzo settore e privato, tenendo conto delle specificità delle diverse popolazioni straniere
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