Scientific Publications of the University of Toulouse II Le Mirail
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How a Tortured Conference Becomes a Series: An Analysis of Conference Manipulations
No full textInternational audienceThe growing publication rate puts an increasing pressure on peer review. Low-quality articles get accepted despite flaws and scientific misconduct. We focus on the case of tortured articles: publications containing paraphrased scientific expressions that we call tortured phrases. These tortured phrases typically result from authors violating scientific norms, who copyparaphrase-paste preexisting text: it is a form of synonym-based plagiarism. In this study, we show that such tortured conference articles tend to cluster within certain recurring conference series. We analyze the organization and characteristics of these conferences to better understand the mechanisms behind their emergence and proliferation
A mathematical framework for modelling order book dynamics
No full text43 p.International audienceWe present a general framework for modelling the dynamics of limit order books, built on the combination of two modelling ingredients: the order flow, modelled as a general spatial point process, and market clearing, modelled via a deterministic 'mass transport' operator acting on distributions of buy and sell orders. At the mathematical level, this corresponds to a natural decomposition of the infinitesimal generator describing the evolution of the limit order book into two operators: the generator of the order flow and the clearing operator. Our model provides a flexible framework for modelling and simulating order book dynamics and studying various scaling limits of discrete order book models. We show that our framework includes previous models as special cases and yields insights into the interplay between order flow and price dynamics
An overview of variance-based importance measures in the linear regression context: comparative analyses and numerical tests
No full textInternational audienceOne of the most fundamental issues in many socio-environmental studies is the identification of causal effects and influential variables related to phenomena of interest. In the context of regression analysis, importance measures are effective tools for feature selection and model interpretation, allowing for the ranking of the most influential regressors. In particular, variance-based importance measures (VIMs) are a prominent topic in the field of statistics, as well as in the emerging field of global sensitivity analysis. This is due to their accessible interpretation as variance shares of the explained variable. This work focuses on the linear regression model and aims to provide an updated overview of the most well-founded methods, mainly from comparative analyses and numerical tests on various toy cases. The paper also addresses some of the practical challenges that arise, including the case of dependent inputs and high input dimensionality. The practical relevance of these tools is demonstrated through empirical studies on simulated data and public datasets. The Supplementary Material also presents the use of VIMs in a classification context, specifically via the logistic linear regression model
Spécificités, aspécificités en thérapie psychanalytique au grand âge
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Learning 3-Manifold Triangulations
No full textInternational audienceReal 3-manifold triangulations can be uniquely represented by isomorphism signatures. Databases of these isomorphism signatures are generated for a variety of 3-manifolds and knot complements, using SnapPy and Regina, then these language-like inputs are used to train various machine learning architectures to differentiate the manifolds, as well as their Dehn surgeries, via their triangulations. Gradient saliency analysis then extracts key parts of this language-like encoding scheme from the trained models. The isomorphism signature databases are taken from the 3-manifolds' Pachner graphs, which are also generated in bulk for some selected manifolds of focus and for the subset of the SnapPy orientable cusped census with initial tetrahedra. These Pachner graphs are further analysed through the lens of network science to identify new structure in the triangulation representation; in particular for the hyperbolic case, a relation between the length of the shortest geodesic (systole) and the size of the Pachner graph's ball is observed
Comment la territorialisation du pilotage de l’orientation permet-elle la redéfinition d’une culture professionnelle commune ?
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Symbolic payment: an issue in the setting of child psychoanalysis
No full textInternational audienceDrawing from a clinical perspective of child psychoanalysis in France, the authors examine the significance of symbolic payment by the child in the latency stage. They refer to Freud’s psychosexual theory to explore the way in which symbolic payment can be used in the transference process. The authors outline points of indication and of contraindications for introducing symbolic payment for sessions by the child. The question of when to introduce this relatively novel treatment parameter should be considered on a case-by-case b
Morse homology with differential graded coefficients
No full text256 pages. v2: Minor modifications and additions to address referee's comments. Change to book format. v3: Minor changeInternational audienceWe develop a theory of Morse homology and cohomology with coefficients in a derived local system, for manifolds and also more generally for colimits of spaces that have the homotopy type of manifolds, with a view towards Floer theory. The model that we adopt for derived, or differential graded (DG) local systems is that of DG modules over chains on the based loop space of a manifold. These encompass both classical (non DG) local systems and chains on fibers of Hurewicz fibrations. We prove that the Morse homology and cohomology groups that we construct are isomorphic to DG Tor and Ext functors. The key ingredient in the definition is a notion of twisting cocycle obtained by evaluating into based loops a coherent system of representatives for the fundamental classes of the moduli spaces of Morse trajectories of arbitrary dimensions. From this perspective, our construction sits midway between classical Morse homology with twisted coefficients and more refined invariants of Floer homotopical flavor. The construction of the twisting cocycle is originally due to Barraud and Cornea with Z/2-coefficients. We show that the twisting cocycle with integer coefficients is equivalent to Brown's universal twisting cocycle. We prove that Morse homology with coefficients in chains on the fiber of a Hurewicz fibration recovers the homology of the total space of the fibration. We study several structural properties of the theory: invariance, functoriality, and Poincar\'e duality, also in the nonorientable case
Renormalised energy between boundary vortices in thin-film micromagnetics with Dzyaloshinskii-Moriya interaction
No full textInternational audienceWe consider a three-dimensional micromagnetic model with Dzyaloshinskii-Moriya interaction in a thin-film regime for boundary vortices. In this regime, we prove a dimension reduction result: the nonlocal three-dimensional model reduces to a local two-dimensional Ginzburg-Landau type model in terms of the averaged magnetization in the thickness of the film. This reduced model captures the interaction between boundary vortices (so-called renormalised energy), that we determine by a Γ-convergence result at the second order and then we analyse its minimisers. They nucleate two boundary vortices whose position depends on the Dzyaloshinskii-Moriya interaction
High-order Sparse-PIC methods: analysis and numerical investigations
No full textInternational audienceParticle-in-cell (PIC) methods embedding sparse grids have been recently introduced to decrease the statistical noise inherent to PIC approximations. In sparse-PIC methods, the numerical noise is filtered out from the approximation thanks to a reconstruction of the grid quantities on a hierarchy of coarse meshes. This procedure introduces a significant gain in the precision of the numerical approximation with respect to the mean number of particles in a grid cell, this parameter controlling the numerical noise, but also introduces a slight discrepancy of the method precision with respect to the mesh resolution. In previous studies, this issue is addressed by a careful tuning of the grids composing the sparse grid hierarchy, to define a trade-off between the gain in the numerical noise and the loss in the grid error. The present work is dedicated to improving the precision of sparse-PIC methods with respect to the mesh resolution and, contrary to the previous achievements, without deteriorating the gains with respect to the statistical noise. A refined error estimate is proposed. It permits one to control the number of numerical particles to obtain a comparable statistical noise in the approximation carried out by either a standard or a sparse-PIC method (and thus assess the true merits of the methods)