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Transformer-based Track Fitting for HL-LHC
No full textInternational audienceAs the High-Luminosity LHC (HL-LHC) era approaches, significant improvements in reconstruction software are required to keep pace with the increased data rates and detector complexity. A persistent challenge for high-throughput event reconstruction is the estimation of track parameters, which is traditionally performed using iterative Kalman Filter-based algorithms. While GPU-based track finding is progressing rapidly, the fitting stage remains a bottleneck. The main slowdown is coming from data movement between CPU and GPU which reduce the benefits of acceleration. This work investigates a deep learning-based alternative using Transformer architectures for the prediction of the track parameters. We evaluate the approach in a realistic setting using the ACTS software framework with the Open Data Detector (ODD) geometry on full simulation and Kalman Filter for baseline comparison, observing promising results
Semi-implicit strategies for the Serre-Green-Naghdi equations in hyperbolic form. Is hyperbolic relaxation really a good idea?
No full textThe Serre-Green-Naghdi (SGN) equations provide a valuable framework for modelling fully nonlinear and weakly dispersive shallow-water flows. However, their elliptic formulation can considerably increase the computational cost compared to the Saint-Venant equations. To overcome this difficulty, hyperbolic models (hSGN) have been proposed that replace the elliptic operators with first-order hyperbolic formulations augmented by relaxation terms, which recover the original elliptic formulation in the stiff limit. Yet, as the relaxation parameter λ increases, explicit schemes face restrictive stability constraints that may offset these advantages.To mitigate this limitation, we introduce a semi-implicit (SI) integration strategy for the hSGN system, where the stiff acoustic terms are treated implicitly within an IMEX Runge-Kutta framework, while the advective components remain explicit. The proposed approach mitigates the CFL stability restriction and maintains dispersive accuracy at a moderate computational cost. Numerical results confirm that the combination of hyperbolization and semi-implicit time integration provides an efficient and accurate alternative to both classical SGN and fully explicit hSGN solvers.</p
Photonic reservoir computing: A thematic review
No full textInternational audienceReservoir computing offers a versatile approach to temporal information processing by exploiting the dynamics of nonlinear systems to enable learning with a linear readout.Photonic hardware is particularly attractive for this paradigm, thanks to ultrafast dynamics and massive parallelism across multiple accessible degrees of freedom of light.In this thematic review, we chart the development of photonic reservoir computing across hardware platforms, from delay-based architectures and integrated photonic circuit implementations to free-space systems.We also discuss how the input and output layers influence the performance of photonic reservoirs.We present the explored learning algorithms that go beyond linear regression, and list some popular benchmark tasks and shed light on some key applications that have been investigated in the literature.Finally, we discuss emerging unconventional implementations.The overall goal of this review is to provide a panoramic overview of photonic reservoir computing, useful for both practitioners and newcomers to the field
Strong-field regime within effective field theory
No full textInternational audienceBuilding upon the Covariant Derivative Expansion, we develop a method to compute effective actions that is able to capture non-perturbative effects induced by strong background fields. We demonstrate the method in scalar QED, by deriving the full second-derivative corrections to the scalar Heisenberg--Euler effective action. The corresponding result is interpreted as an effective field theory with three characteristic scales, two of which are large (mass and field strength) in comparison with the remaining one (derivatives of the field). As an application, we show that, at this order, the transseries structure of the Schwinger pair production rate is preserved, even if the involved coefficients are modified. Our analysis also helps clarify recent disagreements concerning the coefficients of this effective action
Mythes sur les Violences Faites aux Femmes : une étude exploratoire selon l’âge
No full textInternational audienceViolence against women (VAW) sexual or domestic, which is widespread, including among older adults, results from socially shared myths about violence and sexist attitudes. The aim of this study is to identify a possible generational effect in this relationship between adherence to stereotypes about VAW and about gender. Three age groups (18–24 years; 25–64 years; over 65 years; N = 96) completed three questionnaires on acceptance of myths about rape, domestic violence, and sexism (hostile and benevolent). Comparisons between the three age groups show that the “Older Adults” group is characterized by higher acceptance of some myths about VAW: greater blaming of the rape victim, failure to acknowledge or minimizing the reality of domestic violence. Hostile sexism is a significant predictor of VAW myth acceptance (14–51% of variance explained). Benevolent sexism, on the other hand, is a primary specific predictor of endorsement of the “It’s not rape” myth and a secondary predictor of domestic violence victim blaming. Membership of the “Older Adults” group is a central predictor of both domestic violence minimization and rape victim blaming. These exploratory findings are discussed in terms of VAW prevention across the lifespan.Les Violences Faites aux Femmes (VFF) sexuelles ou conjugales, largement répandues y compris chez les personnes âgées, prennent leur source dans des mythes socialement partagés à l’égard des violences et dans des attitudes sexistes. L’objectif de cette étude est d’identifier un éventuel effet de génération dans ce lien entre l’adhésion aux stéréotypes sur les VFF et sur le genre. Trois groupes d’âge (18-24 ans ; 25-64 ans ; plus de 65 ans ; N=96) ont complété trois questionnaires relatifs à l’acceptation des mythes sur le viol, sur les violences conjugales, et du sexisme (hostile et bienveillant). Les comparaisons entre les trois groupes d’âge montrent que le groupe des « Adultes âgés » se distingue par une plus forte acceptation de certains mythes relatifs aux VFF : plus fort blâme de la victime de viol, non-reconnaissance ou minimisation de la réalité des violences conjugales. Le sexisme hostile est un prédicteur significatif de l’adhésion aux mythes sur les VFF (14 à 51 % de la variance expliquée). Le sexisme bienveillant, quant à lui, est un prédicteur spécifique principal de l’adhésion au mythe « Ce n’est pas un viol », et un prédicteur secondaire du blâme de la victime de violences conjugales. L’appartenance au groupe « Adultes âgés » est un prédicteur central dans la minimisation des violences conjugales, et dans le blâme de la victime de viol. Ces résultats exploratoires sont discutés en termes de prévention des VFF à tous les âges de la vie
Porto, entre duas pontes: imagens de um espaço em tensão
No full textInternational audienceThis article engages with the theme of "Multilateral Dialogues" by exploring the tensions and interlocutions that define contemporary Porto (Portugal), a city emblematic of tourism-driven transformations. The study aims to present a critical and visual exploration of the urban tensions between the showcase city and the inhabited city. The methodology is an experimental praxis framed as a "visual archaeology of the present." This praxis is based on an experimental urban walk that combines 360° video, smartphone photography, and 3D photogrammetry. The visual experiment adopts a reflexive "ethno-graphic" approach: the researcher's body is integrated into the image, questioning the stance of the observer as both tourist and critic, and serving as a primary site of interlocution. The main result is a visual essay that does not aim to document the city objectively, but rather to render perceptible the temporal, social, and material strata that constitute Porto's urban landscape. By attending to subtle details, ruins, and spaces, the study offers a situated reading of the conflicts, cohabitations, and (potential) resistances that shape the contemporary Western city. Ultimately, this work foregrounds the complex layering of life, memory, and commodification, revealing a space under the pressures of tourism-driven capitalism as a site of constant confrontation.Este artigo engaja-se com o tema "Diálogos Multilaterais" ao explorar as tensões e interlocuções que definem o Porto contemporâneo (Portugal), uma cidade emblemática das transformações impulsionadas pelo turismo. O objetivo do estudo é apresentar uma exploração crítica e visual das tensões urbanas entre a "cidade vitrine" e a "cidade habitada". A metodologia é uma práxis experimental enquadrada como uma "arqueologia visual do presente". Esta práxis baseia-se numa caminhada urbana experimental que combina vídeo 360°, fotografia com smartphone e fotogrametria 3D. O experimento visual adota uma abordagem "etno-gráfica" reflexiva: o corpo do pesquisador é integrado à imagem, questionando a postura do observador como turista e crítico, e servindo como um local primário de interlocução. O principal resultado é um ensaio visual que não visa documentar a cidade objetivamente, mas sim tornar perceptíveis os estratos temporais, sociais e materiais que constituem a paisagem urbana do Porto. Ao atentar para detalhes sutis, ruínas e espaços, o estudo oferece uma leitura situada dos conflitos, coabitações e (potenciais) resistências que moldam a cidade ocidental contemporânea. Em última análise, este trabalho coloca em primeiro plano a complexa estratificação da vida, memória e mercantilização, revelando um espaço sob as pressões do capitalismo turístico como um local de constante confrontação
A novel framework for phytoplankton biomonitoring: Trait assignment of 23S rRNA sequences
No full textInternational audiencePhytoplankton is a key biological group used to assess the ecological status of lakes in several legislative water management plans. Two cutting-edge approaches for community characterization are DNA metabarcoding and trait-based analyses. While the former provides a fast, cost-effective and high-throughput methodology for identifying communities, the latter reveals the structure of communities through bio-ecological traits. The main aim of this study was to combine these approaches to directly assign traits to amplicon sequence variants. To achieve this, we used the newly developed Phytool v3 reference database. Using an in silico test, we assessed the efficiency and reliability of our approach. We found: (1) that a greater number of sequences with better reliability can be assigned to traits than to genus or species level and (2) that traits are conserved in the phylogeny with varying extent. Then, we tested the usefulness of direct trait assignment on environmental samples from lakes. The test showed a greater number of successfully assigned sequences and a good ecological interpretation of community structures in the different environments. Furthermore, we identified three factors (completeness of the reference library, sequence similarity and the number of neighbours in the reference database) which, depending on the trait under consideration, interfere with the assignment success of our approach. While DNA metabarcoding data can be exploited in many ways depending on the objectives, our study showed that an innovative framework based on direct trait assignment of sequences could overcome gaps in reference databases and further improve our knowledge of phytoplankton community structure
Measurement of the top-quark mass using decays with a meson at 13 TeV with the ATLAS detector
No full textInternational audienceThe top-quark mass is measured using top-quark decays producing an isolated lepton and meson reconstructed in its decay mode. The data sample was recorded with the ATLAS detector in proton-proton collisions at a centre-of-mass energy of TeV during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 140 fb. The measurement is based on the invariant mass of the system made of the isolated lepton from the boson decay and the non-isolated pair from a decay of a -hadron, exploiting its sensitivity to the top-quark mass. An unbinned maximum-likelihood fit to the distribution is performed to extract the top-quark mass. The top-quark mass is measured to be GeV, with a total uncertainty of 1.56 GeV. The third uncertainty arises from changing the dipole parton shower gluon-recoil scheme used in top-quark decays
Can the Dynamo of Spiral-arm Galaxies Be Explained by Anisotropic Conductivity?
No full textInternational audienceThe possibility of generating a magnetic field by a dynamo effect with anisotropic electrical conductivity rather than turbulent flow has been demonstrated theoretically and experimentally. If the electrical conductivity is anisotropic, the electrical currents will flow preferentially in certain directions rather than others, and a simple differential rotation will suffice to generate a magnetic field. In a galaxy with spiral arms, it is reasonable to assume that the electrical conductivity will be twice as large along the arms than in the perpendicular direction, suggesting the possibility of an anisotropic dynamo. However, a further geometrical criterion must be satisfied to obtain a dynamo. It is given by Ω ′ · sin p > 0 , where p is the pitch angle of the spiral arms, with p ∈ [ − π 2 , π 2 ] , and Ω ′ is the radial shear of the angular velocity. We find that the usual spiral-arm galaxies, which satisfy ∣ Ω ′ ∣ < 0 , do not satisfy this dynamo condition because they have trailing arms instead of leading arms. Even galaxy NGC 4622, which has both trailing and leading arms, does not satisfy this dynamo condition either. This is confirmed by numerical simulations of the induction equation. Thus, for all spiral-arm galaxies known to date, the anisotropy of the spiral arms cannot explain the existence of galactic magnetic fields until further notice