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A Kernel Two-Sample Test Invariant under Group Action with Applications to Functional Data
No full textWe introduce a kernel-based two-sample test for comparing probability distributions up to group actions. Our construction yields invariant kernels for locally compact -compact groups and extends classical Haar-based approaches beyond the compact setting. The resulting invariant Maximum Mean Discrepancy (MMD) test is developed in a general framework where the sample space is assumed to be Polish. Under natural conditions, the invariant kernel induces a characteristic kernel on the quotient space, ensuring consistency of the associated MMD test. The method is well suited to functional data, where invariances such as temporal shifts arise naturally, and its effectiveness is illustrated through simulation studies
On the origins and variation of nucleotide skews of archaeal genomes
No full textInternational audienceWe have used nucleotide skews as the proxy to understand the evolution of archaeal genomes. Our genome-wide studies using substantial datasets suggest that translational selection and the nature of the genetic code are universally conserved determinants of asymmetric guanine and cytosine distributions. We propose that in the case of the majority of bacterial chromosomes, mutational processes and/or DNA repair also result in the strand-specific nucleotide skews. This is in stark contrast to what we observe for archaeal chromosomes and plasmids, and reveals that archaea have a greatly reduced ability to create mutations and/or repair DNA damage in a strand-specific manner. We suggest that in the future, the described computational and statistical approach will help to understand the evolutionary dynamics of the archaeal chromosomes through the tree of life
Nonnegativity certificates for finite semi-algebraic sets
No full textWe introduce new certificates for nonnegativity of multivariate polynomials with rational coefficients over zero-dimensional semi-algebraic sets. They are perfectly complete, certifying every nonnegative polynomial, and perfectly sound, correctly identifying negativity. We rely on resultants computations and Rational Univariate Representations (RUR) and make no assumptions on the input.For the univariate case, we introduce a perturbation technique that avoids root approximation and does not alter the (bit)size of the input. For multivariate polynomials, we make a reduction to the univariate case using RUR.For the dense case, we compute a certificate in OB(d 4n+3 (d + τ )) bit operations; it involves numbers of bitsize O(d 3n+2 (d + τ )), where n is the number of variables, d the degree, and τ the maximum coefficient bitsize of the polynomials. For the sparse case, we provide the first sparse certificate based on the Newton polytope Q of the input polynomials. We compute in OB(vol(Q) 8 (n!) 8 2 5n+3 (n + τ )),For semi-algebraic sets with s inequalities, we present two approaches. The first performs a reduction to the algebraic case and has complexity OB(2 (3ω+3)s d 5n τ ); it is purely algebraic approach and does not require root approximation. The second exploits approximate Lagrange interpolation and matches the O(sd 4n τ ) bitsize bounds of recent work by Baldi, Krick, and Mourrain [2] while improving complexity by orders of magnitude and removing all structural assumptions on the input.Additionally, we provide a witness of negativity, ensuring that we either obtain a certificate or it does not exist.</div
System-size dependence of charged-particle suppression in ultrarelativistic nucleus-nucleus collisions
No full textInternational audienceHigh-energy partons lose energy while propagating through the hot, strongly interacting medium produced in ultrarelativistic nucleus-nucleus collisions, leading to a suppression of particle production at high transverse momentum (). The dependence of this energy loss on the size of the colliding nuclear system has yet to be firmly established experimentally. This Letter presents a systematic study of charged-particle suppression across four different nucleus-nucleus collision systems using nuclear modification factors () measured by the CMS Collaboration at the CERN LHC. Previous CMS measurements of in oxygen-oxygen, xenon-xenon, and lead-lead collisions are recast with identical intervals and are complemented by the first measurement of the charged-particle in neon-neon collisions at = 5.36 TeV. The neon-neon data correspond to an integrated luminosity of 0.76 nb. The in all collision systems examined show similar qualitative trends, but have a magnitude which is ordered with the nucleon number A. The feature a downward slope at low , a local minimum at around 57 GeV, and an upward slope with increasing . The are also compared in terms of A, which is proportional to the nuclear radius. Models including only initial-state nuclear effects fail to reproduce the observed trends, whereas energy loss models reproduce the trends in the region 9.6 GeV
Improved Runtime Guarantees for the SPEA2 Multi-Objective Optimizer
No full textInternational audienceTogether with the NSGA-II, the SPEA2 is one of the most widely used domination-based multi-objective evolutionary algorithms. For both algorithms, the known runtime guarantees are linear in the population size; for the NSGA-II, matching lower bounds exist. With a careful study of the more complex selection mechanism of the SPEA2, we show that it has very different population dynamics. From these, we prove runtime guarantees for the ONEMINMAX, LEADINGONES-TRAILINGZEROS, and ONEJUMPZEROJUMP benchmarks that depend less on the population size. For example, we show that the SPEA2 with parent population size µ ≥ n -2k + 3 and offspring population size λ computes the Pareto front of the ONEJUMPZEROJUMP benchmark with gap size k in an expected number of O((λ + µ)n + n k+1 ) function evaluations. This shows that the best runtime guarantee of O(n k+1 ) is not only achieved for µ = Θ(n) and λ = O(n) but for arbitrary µ, λ = O(n k ). Thus, choosing suitable parametersa key challenge in using heuristic algorithms -is much easier for the SPEA2 than the NSGA-II
Comparative Study of the Impacts Resulting from Failures in the Municipal Solid Waste Management System in the Sudano-Sahelian Cities of Cameroon and Associated Environmental Impacts
No full textInternational audienceThe study analyzes the failures of municipal solid waste management systems in the Sudano-Sahelian cities of Cameroon (Maroua, Garoua, and Kousséri) and assesses their environmental impacts. By combining quantitative and qualitative approaches, we demonstrate that the lack of adequate infrastructure, insufficient community awareness, and the inadequacy of effective public policies contribute to adverse consequences for public health, as well as for soil quality, air quality, and water resources. The findings reveal a strong correlation between systemic management dysfunctions and the uncontrolled accumulation of waste, thereby promoting pollution, the spread of diseases, and ecosystem degradation. Based on a comparative diagnostic assessment, practical recommendations are proposed to strengthen local waste management structures, promote circular economy principles, and implement integrated waste management policies.</div
Nucleon tensor form factors at large
No full textInternational audienceWe investigate nucleon tensor form factors in the large- limit. In this picture, the nucleon emerges as a state of the valence quarks, which were bound by pion mean fields that were created by the presence of the valence quarks self-consistently. We find that the tensor charge () and the anomalous tensor magnetic moment () are dominated by valence quarks, while the tensor quadrupole moment () shows significant sea quark effects. We examine how these quantities vary as the average size of the pion mean field is changed, showing interpolation between non-relativistic quark and Skyrme limits. We also observe that and depend weakly on the pion mass. In contrast, exhibits strong enhancement near the chiral limit. The numerical results are in good agreement with available lattice QCD data and provide predictions for unmeasured quantities
Arctic soil carbon insulation averts large spring cooling from surface–atmosphere feedbacks
No full textInternational audienceThe insulative properties of soil organic carbon (SOC) and surface organic layers (moss, lichens, litter) regulate surface–atmosphere energy exchanges in the Arctic through a coupling with soil temperatures. However, a physical description of this process is lacking in many climate models, potentially biasing their high-latitude climate predictions. Using a coupled surface–atmosphere model, we identified a strong feedback loop between soil insulation, surface air temperature, and snowfall. Without insulation, the latent heat needed for soil ice thawing leads to a late spring and summer cold bias in surface air temperature (above 2 °C) over Arctic regions. The integration of soil insulation eliminates this bias and significantly improves the simulation of permafrost dynamics. Our findings, including the potential consequences of large perturbations (e.g., fires), highlight the importance of combining soil water freezing with a physical representation of SOC and surface organic layer insulation in Earth system models, to improve Arctic climate predictions
Observation of the and decays
No full textInternational audienceThe first observation of the decay and the most precise measurement of the branching fraction of the decay are reported, using proton-proton collision data from the LHCb experiment collected in 2016--2018 at a centre-of-mass energy of 13~TeV, corresponding to an integrated luminosity of 5.4~fb. Using the and decays as normalisation channels, the ratios of branching fractions are measured to be: where the first uncertainty is statistical and the second systematic
Diurnal and Seasonal Variations of Gravity Waves in the Lower Atmosphere of Mars as Observed by InSight
No full textInternational audienceWe investigate Gravity Waves (GWs) in the lower atmosphere of Mars based on pressure timeseries acquired by the InSight lander. We compile a climatology showing that most GW activity detected at the InSight landing site takes place after the sunrise and sunset; they are almost absent during the aphelion season, and more prominent around the equinoxes, with variations during dust events and interannual variations. We find GWs with coherent phases in different sols, and a previously unnoticed coincidence of GW activity with those moments in which the diurnal cycle (of tidal origin) exhibits the fastest increases in absolute pressure. We explore the possibility that some of these GWs might actually be high-order harmonics of thermal tides transiently interfering constructively to produce relevant meteorological patterns, and discuss other interpretations based on wind patterns. The so-called Terminator Waves observed on Earth might also explain some of our observations. Plain Language Summary Gravity waves are oscillations in a fluid, observed for example, in the surface of water when it is perturbed. These waves are common in planetary atmospheres and play a key role in their dynamics; however, they are difficult to reproduce in computer models. Based on the comprehensive observations of pressure acquired by the InSight lander, we analyze the occurrence of these waves on Mars at different seasons and times of the day in unprecedented detail. We find that these waves are much more common after the sunrise and the sunset. Also, they tend to repeat synchronously in consecutive days, and they seem to happen at those moments when the absolute atmospheric pressure is increasing. Interpreting these observations is challenging, and we propose various plausible explanations