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Climate Captivity: When in-situ Adaptation and Moving Out Are No Longer Options
No full textInternational audienceThe term captivity describes the condition in which people face increasing exposure to human-made climate disruptions or disaster risks without effective means to mitigate these impacts—whether through in-situ adaptation, mobility, or migration. Captivity offers an alternative to terms such as immobility or trapped, shifting the focus toward the root causes of why people remain in potentially uninhabitable places. This article establishes captivity as an analytical framework to examine the diverse reasons and consequences of prolonged environmental risk exposure. It also challenges the implicit assumption in climate migration and adaptation research that affected individuals are responsible for not leaving sooner or making the “right” choices. Rather than ceasing their efforts to adapt or relocate, captive individuals often experience repeated failures in their attempts to reduce vulnerability, leading to maladaptation over time. Although empirical findings remain fragmented across different fields and are frequently marginalized through the uncritical deployment of terminology, the outward projection of threats, whether by displacing risk spatially, temporally, or cognitively, may constitute the sole remaining coping mechanism as environments become progressively uninhabitable. By conceptualizing captivity, we aim to deepen understanding of the lived experiences, decision-making processes, and daily struggles of those caught in worsening environmental conditions
Simulation expérimentale des phénomènes de mobilité augmentés par les échappements gazeux à basse pression atmosphérique
No full textInternational audiencePlanetary surfaces are transformed by various processes at different atmospheric pressures. On Mars, fluids are expected to have flowed at reduced atmospheric pressure during the last 3 billion years. Nevertheless, the influence of low pressure on surface processes has been investigated in only a few studies. Our understanding of the influence of gas in fluids on Martian surface morphologies is poor due to the low number of experiments performed at low atmospheric pressure (∼7 mbar) and the limited potential analogs on Earth. Here, we present laboratory and numerical experiments to explore the influence of gas production on fluid-sand mobility at low atmospheric pressure. Energetic cohesive sand pellets uplifted by escaping gas were generated, forming narrow channels with levees with lengths of 80-90 cm, which were approximately 1800 times their widths. The maximum experimentally determined velocity of the pellets ranged from 60 to 150 cm/s. The channel morphologies were formed by a pseudo-levitation mechanism corresponding to transport with reduced friction. We propose that the mechanisms observed in our experiments at low atmospheric pressure may explain some past Martian surface changes.Les surfaces planétaires sont transformées par différents processus de surface générant parfois une mobilité accrue. A basse pression atmosphérique, comme sur Mars lors des 3 derniers milliards d’années, la propagation des fluides à la surface en a été affectée. Cependant, les modes de transport à basse pression (7 mbar) ont été étudiés dans un nombre limité d’expérimentation, ce qui limite notre compréhension précise des écoulements de surface et des morphologies produites par ces processus. Notre connaissance de ce type d’écoulement est d’autant plus faible qu’il n’existe pas d’analogues évidents actuellement à la surface de la Terre. Dans cette étude, nous présentons des résultats expérimentaux et de modélisation sur le transport de matériel solide en présence d’échappements gazeux à basse pression. La propagation d’un mélange cohésif de sable humide, subissant une lévitation partielle causée par la vaporisation de l’eau au contact d’une surface granulaire, génère la formation d’un chenal érosif d’une longueur de 80–90 cm, de levées latéral et frontal à une vitesse comprise entre 60 et 150 cm/s. Ce phénomène est assimilable à une propagation avec une friction basale réduite, mais non nulle . Ce processus de transport et d’érosion pourrait s’être produit ou se produire encore à la surface de Mars
Experimental and numerical simulation study on the thermal performance of building envelope structures incorporating the solid-solid phase change material
No full textInternational audienceThis work is an experimental and numerical study of the thermal performance of building envelope structures incorporating a solid-solid phase change material (S-S PCM), consisting in a cross-linked polyurethane designated as PUX-1500-20. This S-S PCM is capable of storing and releasing thermal energy via phase transitions within the human comfort temperature range, facilitating the temporal and spatial transfer of solar energy for optimizing energy efficiency. The primary aim of this work is to integrate the S-S PCM into hollow bricks used in building envelopes and to evaluate their thermal inertia through both experimental testing and numerical simulation. The experimental results demonstrate that the integration of the PCM effectively delays and decreases the indoor temperature peak. The simulation results also show that the incorporation of the S-S PCM into hollow bricks gives rise to a phase shift of 7 hours and a decrement factor of 0.38. In comparison with the thermal behavior of the building envelopes (hollow brick) without PCMs, our results provide convincing evidence of the important thermal inertia of these structures incorporating the PCMs, revealing their significant potential in reducing energy consumption of building.</div
Anticoncentration in Clifford Circuits and Beyond: From Random Tensor Networks to Pseudomagic States
No full textInternational audienceAnticoncentration describes how an ensemble of quantum states spreads over the allowed Hilbert space, leading to statistically uniform output probability distributions. In this work, we investigate the anticoncentration of random Clifford circuits toward the overlap distribution of random stabilizer states. Using exact analytical techniques and extensive numerical simulations based on Clifford replica tensor networks, we demonstrate that random Clifford circuits fully anticoncentrate in logarithmic circuit depth; namely, higher-order moments of the overlap distribution converge to those of random stabilizer states. Moreover, we investigate the effect of introducing a controlled number of non-Clifford (magic) resources into Clifford circuits. We show that inserting a polylogarithmic in qudit number of T states is sufficient to drive the overlap distribution toward the Porter-Thomas statistics, effectively recovering full quantum randomness. In short, this fact presents doped tensor networks and shallow Clifford circuits as pseudomagic quantum states. Our results clarify the interplay between Clifford dynamics, magic-state injection, and quantum complexity, with implications for quantum circuit sampling, many-body quantum physics, and the benchmarking of quantum computational advantage
Lithium as a Key Tracer of Magmatic Processes: Insights from Experimental Petrology and the Minoan Eruption of Santorini
No full textInternational audienceStable isotopes play a key role in understanding magmatic processes, from crustal differentiation to fluid-magma interactions. In this context, lithium (Li), a highly mobile element sensitive to pressure and temperature variations, serves as an excellent tracer for constraining the rapid dynamics of magma ascent and degassing in felsic systems. This study investigates the behavior of Li in different phases—plagioclase, melt, and fluid—using a combined approach of experimental petrology (equilibrium crystallization experiments) and natural sample analysis. These investigations provide new insights into the partitioning of Li between solid, liquid, and fluid phases under magmatic conditions (50-150 MPa, 800-875 °C) and quantify the partition coefficients between plagioclase, melt, and fluids. This provides key information on the effects of decompression, cooling, and fluid-magma interactions, as well as the interpretation of Li analyses.The Minoan eruption of Santorini (~3600 years BP) serves as an ideal case study to test the application of Li as a tracer of magmatic processes. Lithium gradients in plagioclase crystals suggest an interaction with a chloride-rich brine phase occurring shortly before the eruption. Diffusion modeling indicates that these processes took place over extremely short timescales, from a few seconds to several tens of minutes before the eruption. These findings highlight the potential of Li for constraining both pre- and syn-eruptive processes and their timescales.This study builds on recent advances in the application of stable isotopes to volcanic and magmatic processes, extending their use to the quantification of magma ascent timescales. It underscores the value of experimental and natural studies in refining our understanding of high-temperature magmatic processes and fluid-magma interactions in crustal reservoirs
Tetrahedral Core in a Sea of Competing Magnetic Phases in Graphene
No full textWe reveal the emergence of a robust tetrahedral magnetic ground state in monolayer graphene doped to the van Hove singularity (vHS). This noncoplanar, gapped spin configuration - featuring four orthogonal moments - has been previously identified as a candidate instability. Here, not only do we confirm its stability across all finite interactions using fully self-consistent, real-space-resolved calculations, but we also go beyond earlier work by charting the full surrounding phase diagram. In doing so, we unravel a cascade of symmetry-broken magnetic states - pseudo-tetrahedral, planar, collinear, and modulated textures - which we classify using spin structure factors and vector order parameters. These results stem from unrestricted Hartree-Fock simulations on large supercells with dense k-point sampling, enabling us to resolve interaction-driven magnetic and charge inhomogeneities. Our findings connect directly with recent ARPES and doping experiments near the vHS in graphene, and establish the tetrahedral state as the central correlated instability in this regime, offering predictive insight into emergent magnetism in correlated Dirac materials
Structures internes des dépôts de transport en masse du Cône sous-marin de l'Amazone : en quoi nous renseignent-elles sur les processus de mise en place des glissements sous-marins ?
No full textInternational audienceLes glissements sous-marins sont un processus de premier ordre qui affecte et façonne les marges océaniques du monde entier, impliquant le transfert de volumes variables de sédiments. Les plus grands glissements connus (10 à 2000 km3) sont retrouvés sur les marges continentales passives, caractérisées par une faible activité sismique et de faibles pentes (généralement < 2◦). Malgré celles-ci, les masses remobilisées peuvent se déplacer sur plusieurs dizaines voire centaines de kilomètres. Afin de comprendre leurs mécanismes de mise en place, nous avons analysé huit carottes de type Calypso collectées sur le haut de la pente continentale du Cône sous-marin de l’Amazone, à environ 50 km en aval de la zone de déclenchement, pendant la campagne AMARYLLIS-AMAGAS I (2023). Les limites des dépôts de transport en masse (MTD) ont été définies par la reconnaissance de structures de déformation dans les carottes puis par corrélation avec les profils Chirp. Les déformations ont été identifiées à partir des descriptions visuelles, des photographies et/ou des images rX. Ce travail a été effectué dans le cadre du projet ANR MEGA. Cinq classes de déformation ont été définies. La classe 1 comprend des structures de boudinage et des "écailles" centimétriques imbriquées illustrant un intense cisaillement associé à un faible déplacement horizontal. La classe 2 correspond à des dépôts hémipélagiques basculés de 5-40◦ et fortement micro-fracturés. La classe 3 comprend des structures plissées de taille centimétrique/plurimétrique, impliquant une rhéologie visqueuse et une absorption d’énergie associée à une décélération du MTD. La classe 4 correspond à des dépôts hémipélagiques sub-horizontaux mais intensément micro-fracturés et interprétés comme des mégablocs encore non désintégrés. La classe 5 présente des clastes arrondis flottant dans une matrice argileuse qui caractérisent le faciès débrite et le plus fort degré de déformation. Au sein des MTD, un motif classique de déformations comprend la superposition de bas en haut des classes 1 à 4 ou celle des classes 5 et 4 ou 1, 5 et 4. Ces motifs pouvant être superposés plusieurs fois, les MTD résulteraient d’une mise en place par gel successif de leur partie basale ou de la superposition d’épisodes de rupture/glissement distincts
Géographies différenciées des pratiques habitantes de renaturation des sols urbains
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“Semina: Wallace Berman’s Art of Dis-/In-semination”
No full textInternational audienceThe intermediate terminology has been employed to stress the innovative or transgressive the potential of artworks that articulate their message in the interstices between two or more media forms (Bruhn Jensen 2016, 1).Between 1955 and 1964, Wallace Berman – a visual artist, often considered as the progenitor of the Los Angeles/ San Francisco postwar underground/ countercultural assemblage nexus of the 1950s-60s that took off from a symbolist, surrealist heritage – produced and printed a small-scale, handmade and hand-assemblaged little magazine of unusual format, Semina. The nine issues of this intermedial ephemeral artefact have their singularity, focus and format. They comprised photographs, poems, fragments of prose, drawings and collages by various artists of Berman’s literal and imaginative circle of friends. Semina is an example of the collaborative and collective nature of the West Coast postwar underground world where alternative modes of producing, displaying and disseminating art were gradually delineating the contours of precarious, ephemera modes of experiencing art and literature in the context of the political rhetoric of the Cold War.A small printing of 200 copies each, the intermedial mail art publication was meant to be disseminated among friends and beyond and to inseminate, i.e. influence, other artists and poets. This paper will examine the singularity of these ephemeral objects as well as the environment that gave birth to them and the experiences they elicited. If Semina allowed Berman to investigate the tension between word and image, challenge the very stability of meaning and investigates the potentiality of fragmentation, what narrative was Berman dialogically challenging through materiality and intertextuality? What space was he trying to map? Berman’s intermedial publication is a means to reject any unified or stable subject, Semina’s composition, based on fragments, visual or textual, paired or singled, definitely enter a landscape of signs guided by a single doctrine / mantra “Art is Love is God” and a cryptic letter, the Aleph. How this collage of voices, visual and textual, its very format, bound or in separate leaves or cards, worked at defying chaos and crisis by heralding the ephemeral, the chance decision, the arcane, through this heterotopic and alternative space the magazine becomes is what this paper will try to address
Ecologization and transformation of work at the meso and micro levels of transition: findings from two territorial food projects in France
No full textInternational audienceThis article analyses the links between the ecologization of food systems and transformations of work in two Territorial Food Projects in France. Three case studies are explored, based on a reflective analysis conducted by the researchers: the governance of a Territorial Food Project; the management of a sustainable food offer in mass catering; and the project to replace plastic containers in a central kitchen. For each case, an ergonomics-based iterative methodology was used, drawing on observations, semi-structured interviews, working groups, and reflective workshops. The results reveal how workers act as essential mediators between the macro level (the Territorial Food Project and related laws), the meso level (collective action in local projects) and the micro level (the activity of actors in the food system)