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Unfoldings and coverings of weighted graphs
No full textCoverings of undirected graphs are used in distributed computing, andunfoldings of directed graphs in semantics of programs. We study these twonotions from a graph theoretical point of view so as to highlight theirsimilarities, as they are both defined in terms of surjective graphhomomorphisms. In particular, universal coverings and complete unfoldings areinfinite trees that are regular if the initial graphs are finite. Regularitymeans that a tree has finitely many subtrees up to isomorphism. Two importanttheorems have been established by Leighton and Norris for coverings. We provesimilar statements for unfoldings. Our study of the difficult proof of Leighton's Theorem lead us to generalizecoverings and similarly, unfoldings, by attaching finite or infinite weights toedges of the covered or unfolded graphs. This generalization yields a canonicalfactorization of the universal covering of any finite graph, that (provably)does not exist without using weights. Introducing infinite weights provides uswith finite descriptions of regular trees having nodes of countably infinitedegree. We also generalize to weighted graphs and their coverings a classicalfactorization theorem of their characteristic polynomials
Introduction
No full textLes Doctoriales de l’Europe médiane, de l’espace russe et (post)soviétique, organisées par le Centre de recherche Europes-Eurasie (CREE) en juin 2021, ont réuni des doctorants et jeunes chercheurs autour du thème des archives, considérées à la fois comme outil et objet de recherche. Cette thématique, qui recouvre plusieurs disciplines et concerne plusieurs étapes de l’élaboration d’une thèse, a permis d’enclencher une réflexion fructueuse des participants sur leurs propres pratiques de recherche. Ayant pour objectif de mettre en valeur les travaux de jeunes chercheurs francophones qui contribuent à découvrir des archives inédites, mais aussi à renouveler le regard porté sur des documents déjà étudiés, cette publication entend également contribuer aux études interdisciplinaires des archives et de leurs usages dans les espaces d’Europe centrale et orientale et de l’ex-URSS
Optimization of a dynamic absorber with nonlinear stiffness and damping for the vibration control of a floating offshore wind turbine toy model
No full textPassive vibration mitigation of offshore wind turbines using nonlinear absorbers or nonlinear energy sinks has started to receive attention in the literature. In most cases, little attention has been paid to the possibility of detached resonances that occur when the nonlinear energy sink is attached to the linear system describing the wind turbine. Sea motions that alter the initial conditions of the floating offshore wind turbine may cause the nonlinear energy sink to operate at one or more detached resonances, completely negating its ability to control turbine vibration. In this paper, we are interested in optimizing the parameters of a nonlinear energy sink with nonlinear stiffness and nonlinear viscous damping for vibration control of a toy model (e.g., a linear mass-spring-damper system) of a floating offshore wind turbine over its entire operating range. The mechanism of cancellation of the detached resonance is studied analytically under 1:1 resonance. It is shown that the nonlinear energy sink with properly tuned nonlinear viscous damping allows the complete elimination of undesired regimes and completely restores the absorber's ability to strongly limit the vibration of a floating offshore wind turbine over its entire forcing range. The results obtained over a wide range of parameters suggest that both the optimal nonlinear energy sink parameters (linear and nonlinear stiffness and nonlinear damping) and the damping of floating offshore wind turbine vibration depend on simple power laws of nonlinear energy sink mass and linear damping
On triviality of uniform Diophantine exponents of lattices
No full textIn this paper we prove that uniform Diophantine exponents of lattices attainonly trivial values
Science, identité et droit: Croiser la conceptualisation et l’opérationnalisation de la race et de l’ethnicité
No full textPour une publication sur Épisiciences.The comparative legal scholar authors, working a broad project mapping how law conceptualizes and operationalizes race, ethnicity and nationality, provide an assessment of the triadic relationship between law, identity (making and claims recognition) and science. The project focuses on race and ethnicity, excluding the discussion of gender identity, but the latter is used as a point of reference to demonstrate the transformative changes in the past years in how the meaning of the terms of identity are assigned and conceptualized in social sciences and humanities, and to a certain degree in politics and law. Yet, there is a debilitating lack of linguistic and conceptual resources, cultural tools, and a solid and proper vocabulary for thinking about racial identity, which is particularly stark in the field of law, especially international law, which habitually operates with the concepts of race, ethnicity, and nationality when setting forth standards for the recognition of collective rights or protection from discrimination, establishing criteria for asylum, labeling actions as genocide, or requiring a “genuine link” in citizenship law, without actually providing definitions for these groups or of membership criteria within these legal constructs. The paper provides an overview of the obstacles, challenges and controversies in the legal institutionalization. In technical terms, the operationalization of ethnic/racial/national group affiliation can follow several options: self-identification; authority given to elected or appointed members (representatives) of the group (leaving aside legitimacy-, or ontological questions regarding the authenticity or genuineness of these actors); classification by outsiders, through the perception of the majority; or by outsiders but using “objective” criteria, such as names, residence, et cetera. The paper also provides an assessment of how “objective” criteria, data and constructions provided by science translate into the legal discourse. Case studies will be used from anthropological/historical “scientific knowledge,” and the operationalization of (performative) whiteness and otherness in the US, to contemporary examples of requiring DNA-heritage certificates in naturalization and Diaspora-programs (for example for birthright schemes in Israel); race-focused forensic datasets; and race-based medicine and reproductive technologies – where the methodology and conceptualization of “scientific race” is analyzed in a comparative and critical framework.Les auteurs, juristes comparatistes, travaillant sur un vaste projet qui cartographie la manière dont le droit conceptualise et opérationnalise la race, l’ethnicité et la nationalité, fournissent une évaluation de la relation triadique entre le droit, l’identité (la reconnaissance de l’identité et des revendications) et la science. Le projet se concentre sur la race et l’ethnicité, excluant la discussion de l’identité de genre, mais cette dernière est utilisée comme point de référence pour démontrer les changements transformateurs de ces dernières années dans la façon dont la signification des termes d’identité est assignée et conceptualisée dans les sciences sociales et humaines, et dans une certaine mesure dans la politique et le droit. Pourtant, il existe un manque débilitant de ressources linguistiques et conceptuelles, d’outils culturels et d’un vocabulaire solide et approprié pour réfléchir à l’identité raciale, ce qui est particulièrement flagrant dans le domaine du droit, notamment le droit international, qui utilise habituellement les concepts de race, d’ethnicité et de nationalité lorsqu’il établit des normes pour la reconnaissance des droits collectifs ou la protection contre la discrimination, qu’il établit des critères pour l’asile, qu’il qualifie des actions de génocide ou qu’il exige un « lien authentique » dans le droit de la citoyenneté, sans réellement fournir de définitions pour ces groupes ou de critères d’adhésion dans ces constructions juridiques. L’article donne un aperçu des obstacles, des défis et des controverses liés à l’institutionnalisation juridique. En termes techniques, l’opérationnalisation de l’affiliation à un groupe ethnique/racial/national peut suivre plusieurs options : auto-identification ; autorité donnée aux membres (représentants) élus ou nommés du groupe (en laissant de côté les questions de légitimité ou ontologiques concernant l’authenticité ou l’authenticité de ces acteurs) ; classification par des personnes extérieures, à travers la perception de la majorité ; ou par des personnes extérieures mais en utilisant des critères « objectifs », tels que les noms, la résidence, etc. L’article fournit également une évaluation de la manière dont les critères, données et constructions « objectifs » fournis par la science se traduisent dans le discours juridique. Des études de cas seront utilisées, allant de la « connaissance scientifique » anthropologique/historique et de l’opérationnalisation de la blancheur (performative) et de l’altérité aux États-Unis, à des exemples contemporains d’exigence de certificats d’héritage ADN dans les programmes de naturalisation et de diaspora (par exemple pour les programmes de droit de naissance en Israël) ; des ensembles de données médico-légales axées sur la race ; et de la médecine et des technologies de reproduction fondées sur la race – où la méthodologie et la conceptualisation de la « race scientifique » sont analysées dans un cadre comparatif et critique
L’archeologia a supporto delle identità nazionali: perché distruggere le collezioni di calchi di arte antica?
No full textPour une publication sur Épisciences.Following the example of Germany and after 1870s, plaster casts of ancient art are subject to a “cultural transfer” in France and in Italy. This kind of process reflects the birth of archaeology as a science; it is aligned to a specific change in higher education and it allows a nation building / re-building (by referring to Italian and French examples). In addition, the consolidating nation process is based on a cultural mechanism caused by globalization, i.e. “inventing tradition”. The “myth of white Greece” or that of “Romanity” can be taken into account in order to justify the destruction of plaster casts of ancient art.À l’instar de l’Allemagne et à partir des années 1870, le moulage d’art antique fait l’objet d’un véritable « transfert culturel » en France et en Italie. Ce processus qui témoigne de l’émergence de l’archéologie en tant que science, s’insère dans le cadre plus vaste d’une modification de l’enseignement supérieur et d’une construction (dans le cas de l’Italie) ou d’un redressement de la nation (en France). Cependant, le processus de consolidation de l’État-nation se fonde sur un autre mécanisme culturel engendré par la mondialisation‑globalisation, à savoir l’« invention de la tradition ». Tels sont les cas notamment du « mythe de la Grèce blanche » ou de celui de la « Romanité » qui peuvent offrir des arguments suffisants pour justifier la destruction des collections de moulages d’art antique.Sul modello della Germania e a partire dagli anni ’70 del XIX sec. il calco di arte antica è oggetto di un vero e proprio «transfert culturale» in Francia e in Italia. In particolare, tale transfert segna la nascita dell’archeologia come scienza e s’inserisce nel quadro più ampio di una modifica dell’insegnamento superiore e di una (ri)costruzione della nazione (rispettivamente in Italia e in Francia). Inoltre, il processo di consolidamento dello Stato-nazione si basa su un secondo meccanismo culturale causato dalla mondializzazione‑globalizzazione, ovvero l’«invenzione della tradizione». Un esempio è dato soprattutto dal «mito della Grecia bianca» e da quello della «Romanità» che possono offrire degli argomenti sufficienti a giustificare la distruzione delle collezioni di calchi di arte antica
Inferring Symbolic Automata
No full textWe study the learnability of symbolic finite state automata (SFA), a modelshown useful in many applications in software verification. Thestate-of-the-art literature on this topic follows the query learning paradigm,and so far all obtained results are positive. We provide a necessary conditionfor efficient learnability of SFAs in this paradigm, from which we obtain thefirst negative result. The main focus of our work lies in the learnability ofSFAs under the paradigm of identification in the limit using polynomial timeand data, and its strengthening efficient identifiability, which are concernedwith the existence of a systematic set of characteristic samples from which alearner can correctly infer the target language. We provide a necessarycondition for identification of SFAs in the limit using polynomial time anddata, and a sufficient condition for efficient learnability of SFAs. From theseconditions we derive a positive and a negative result. The performance of alearning algorithm is typically bounded as a function of the size of therepresentation of the target language. Since SFAs, in general, do not have acanonical form, and there are trade-offs between the complexity of thepredicates on the transitions and the number of transitions, we start bydefining size measures for SFAs. We revisit the complexity of procedures onSFAs and analyze them according to these measures, paying attention to thespecial forms of SFAs: normalized SFAs and neat SFAs, as well as to SFAs over amonotonic effective Boolean algebra. This is an extended version of the paperwith the same title published in CSL'22.Comment: arXiv admin note: text overlap with arXiv:2011.0538
Uniform K-stability of polarized spherical varieties
No full textWe express notions of K-stability of polarized spherical varieties in termsof combinatorial data, vastly generalizing the case of toric varieties. We thenprovide a combinatorial sufficient condition of G-uniform K-stability bystudying the corresponding convex geometric problem. Thanks to recent work ofChi Li and a remark by Yuji Odaka, this provides an explicitly checkablesufficient condition of existence of constant scalar curvature Kahler metrics.As a side effect, we show that, on several families of spherical varieties,G-uniform K-stability is equivalent to K-polystability with respect toG-equivariant test configurations for polarizations close to the anticanonicalbundle.Comment: with an appendix by Yuji Odaka, v2 taking into account referee's comments and correcting minor mistakes, v3 EPIGA journal versio
From Books to Knowledge Graphs
No full textThe digital transformation of the scientific publishing industry has led todramatic improvements in content discoverability and information analytics.Unfortunately, these improvements have not been uniform across research areas.The scientific literature in the arts, humanities and social sciences (AHSS)still lags behind, in part due to the scale of analog backlogs, the persistingimportance of national languages, and a publisher ecosystem made of many, smallor medium enterprises. We propose a bottom-up approach to support publishers increating and maintaining their own publication knowledge graphs in the opendomain. We do so by releasing a pipeline able to extract structured informationfrom the bibliographies and indexes of AHSS publications, disambiguate,normalize and export it as linked data. We test the proposed pipeline onBrill's Classics collection, and release an implementation in open source forfurther use and improvement
Lehmann’s Analytical Inconsistencies on Liberalism and Capitalism
No full textReview of Lehmann, P.-J., Liberalism and Capitalism Today, London, Hoboken: ISTE-Wiley, 2021, 214 pp, ISBN 978-1-78630-689-