Portail HAL du Collège de France
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Valéry au Collège de France
No full textInternational audienceAprès la parution en 2023 du Cours de poétique de Paul Valéry, jusque-là resté inédit, Valéry au Collège de France propose la première synthèse et réflexion historique, philosophique et critique sur l’enseignement donné par l’écrivain au Collège de France de 1937 à 1945. Pour la première fois, des spécialistes dressent le bilan de l’édition du Cours et donnent une lecture et interprétation de son enseignement durant les huit années de la chaire de Poétique. Pour la première fois également est proposée une étude d’ensemble de la réception de la pensée de Valéry par des professeurs du Collège de France aujourd’hui disparus et qui furent de grandes figures du XXe siècle – Maurice Merleau-Ponty, Roland Barthes, Yves Bonnefoy et Jacques Bouveresse –, réception qui se poursuit ici à travers les voix de Jean-Pierre Changeux, Antoine Compagnon, Carlo Ossola et Claudine Tiercelin. Cet ouvrage montre à quel point Valéry représente un moment important de l’histoire des idées au XXe siècle, mais aussi de l’histoire intellectuelle du Collège de France
Convergent iridescence and divergent chemical signals in sympatric sister-species of Amazonian butterflies
No full textInternational audienceClosely-related species are often partitioned into different geographic areas or micro-habitats as a result of competition and reproductive interference. Here, we investigate how the evolution of shared adaptive traits may shape ecological interactions and genetic divergence, and facilitate coexistence in sympatry. In closely-related Morpho butterfly species living in the understory of the neo-tropical rainforest, the blue iridescent coloration of the wings is likely involved in predation evasion as well as in mating recognition and courtship. These contrasted selective pressures acting on this visual trait shared between closely-related species has likely shaped their coexistence. We used spectrophotometry, behavioral experiments, visual modeling and chemical analyses applied to samples from allopatric and sympatric populations of Morpho helenor and Morpho achilles to characterize how the evolution of visual and chemical traits might favor their coexistence in sympatry: we quantified the differences in wing iridescence and tested for variations in the sexual preference for this trait between allopatric vs. sympatric populations. We found a strong similarity in iridescence among species in sympatry, suggesting convergence driven by predation. Although behavioral results suggest that iridescent signals could also be used as visual cues during mate choice, convergent iridescent signals may impair the visual recognition of sympatric Morpho species. In contrast, divergent chemical bouquets among species suggest that the visual similarity of sympatric Morpho species might have favored the divergence of alternative traits involved in species recognition such as chemical cues. This study underlines how ecological interactions and trait evolution can shape species coexistence in sympatry. Significance StatementBy changing the visual aspect of animals in movement, iridescence likely impacts multiple visual interactions within and among species, and might therefore shape ecological interactions and species diversification in sympatry. Here we study the relative importance of predation-driven mimicry and sexual selection on the evolution of iridescence on the wings of sister-species of Morpho butterflies. We finely quantify this conspicuous wing phenotype and used behavioral experiments to test whether the sexual preference for this trait can vary between allopatric and sympatric populations of sister-species. We find that convergent iridescence in sympatric Morpho species, putatively driven by predators and supporting the hypothesis of evasive mimicry, impairs species recognition and could promote the divergence in alternative chemical cues involved in mate discrimination.</div
Modern Maths for Ancient Odes: The Commentarial Layers of the <i>Maoshi zhengyi</i> on the Eclipse in “Shiyue zhi jiao”
No full textInternational audienceThis article discusses the commentators, commentarial layers, knowledge and argumentation in Kong Yingda’s (584–648) treatment of the ode “Shiyue zhi jiao” in the Maoshi zhengyi (643). Much had changed between Zheng Xuan (127–200) and Kong Yingda’s day as concerned the Han (202 B.C. – A.D. 220) world order, the feasibility of its “cosmological synthesis” in the sciences, and man’s understanding of eclipses, such as feature in this ode. Kong’s subcommentary to Zheng’s commentary thus provides a stratigraphic cross-section of these changes and an authoritative example of how historical change and scientific progress was to be reconciled with ancient scripture
Constraints on the Pre-Big Bang scenario from a cosmological interpretation of the NANOGrav data
No full textInternational audienceWe discuss a recently proposed interpretation of the signal detected by the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) as due to a relic stochastic background of primordial gravitons, produced in the context of the string cosmology pre-big bang scenario. We show that such interpretation cannot be reconciled with a phenomenologically viable minimal version of such scenario, while it can be allowed if one considers an equally viable but generalised, non-minimal version of pre-big bang evolution. Maintaining the -duality symmetry throughout the high-curvature string phase is possible although somewhat disfavoured. The implications of this non-minimal scenario for the power spectrum of curvature perturbations are also briefly discussed
Climate and Environment in the Development of Modern Japanese Housing. From Architects’ Initial Interest in Housing to Fujii Kōji
No full textInternational audienceFujii Kōji, considered the pioneer of modern Japanese housing, was the first Japanese architect to design houses based on a scientific study of climate. Conducted in the 1920s, his study is closely related to matters of taste and is part of a dual process: the pursuit of a Japanese dwelling suited to the Japanese climate and cultural tastes. Understanding Fujii Kōji's place in this process, especially when compared to the first Japanese housing theorist, Yasuoka Katsuya, sheds light on the significance of climate in the development of modern Japanese housing. This paper explores the role of climate and the environment in the emergence of eclectic Western Japanese housing, the rise of Western-style housing, and Yasuoka's quest for an ideal housing suitable for modern Japan. This analysis highlights Fujii's innovative thinking and reveals its unique characteristics. While his architectural philosophy shares many similarities with Yasuoka's, his scientific approach to climate as the foundation for architectural design was truly innovative
Room-temperature efficient single-photon generation from CdSe/ZnS nanoplateletes
No full textInternational audienceIn the search for materials for quantum information science applications, colloidal semiconductor nanoplatelets (NPLs) have emerged as a highly promising new class of materials due to their interesting optical properties, such as narrow emission linewidth and fast photoluminescence (PL) lifetimes at room temperature. So far only few works focused on the quantum properties of their emission, however, NPLs, with their atomic-scale thickness and one-dimensional quantum confinement, are promising candidates for single-photon sources. Here, we demonstrate room-temperature single-photon emission from core/shell CdSe/ZnS NPLs, which feature 820 nm surface area and 1 nm shell. The limited surface area ensures effective Auger non-radiative recombination, resulting in highly efficient single-photon generation with values of photon purity as low as . The observed long-period blinking and bleaching, typical of such thin shells, can be easily reduced by increasing the shell thickness. This work establishes NPLs as new single-photon sources very well suited for integration into quantum photonic systems
Le roman policier japonais, entre démocratie balbutiante et montée du militarisme (1923-1945)
No full textInternational audienceJapanese crime fiction enjoyed a golden age in the 1920s and 1930s, with the emergence of a first generation of writers who established an “indigenous” genre while intense debates about its definition erupted. Yet this effervescence should not conceal a growing malaise: Shupio, the last specialist detective magazine, folded in 1938, and some writers turned to less politically problematic genres (espionage, adventure, science fiction). The Japanese detective genre is thus highly dependent on the political context in the archipelago. The birth of the detective fiction field at the end of the 19th century was symbolized by a very democratic freedom: authors created works that sometimes departed greatly from the literary canons of the genre. This effervescence was challenged by the rise of militarism from the 1930s onwards. But while the organisational structure disappeared at the same time as democracy in the early 1940s, examples show that some writers tried to get other messages across, going against the war-mongering and anti-democratic rhetoric.Le roman policier japonais connaît un âge d’or pendant les décennies 1920 et 1930, avec l’émergence d’une première génération d’écrivains qui mettent en place un genre « autochtone » tandis qu’éclatent d’intenses débats à propos de sa définition. Pourtant, cette effervescence ne doit pas cacher un malaise grandissant : Shupio, la dernière revue policière spécialisée, se saborde en 1938, et certains écrivains se tournent vers des genres politiquement moins problématiques (espionnage, aventure, science-fiction). Le genre policier japonais est ainsi fortement dépendant du contexte politique de l’archipel. La naissance du champ du roman policier à la fin du XIXe siècle est symbolisée par une liberté toute démocratique : les auteurs créent des œuvres qui s’éloignent parfois fortement des canons littéraires du genre. Cette effervescence est remise en cause par la montée du militarisme à partir des années 1930. Mais si la structure organisationnelle disparaît en même temps que la démocratie au début des années 1940, des exemples montrent que certains écrivains tentent de faire passer d’autres messages, allant à l’encontre des discours bellicistes et anti-démocratiques
The Close AGN Reference Survey (CARS) : a comparison between sub-mm and optical AGN diagnostic diagrams
No full textInternational audienceThe LIR –LHCN relation suggests that there is a tight connection between dense gas and star formation. We use data from the Close AGN Reference Survey (CARS) to investigate the dense gas – star formation relation in active galactic nuclei (AGN) hosting galaxies, and the use of dense gas as an AGN diagnostic. Our sample contains five Type-1 (unobscured) AGN that were observed with the Atacama Large Millimetre/submillimetre Array with the aim to detect HCN(4-3), HCO+ (4-3), and CS(7-6). We detect the dense gas emission required for this analysis in three of the five targets. We find that despite the potential impact from the AGN on the line fluxes of these sources, they still follow the LIR –LHCN relation. We then go on to test claims that the HCN/HCO+ and HCN/CS line ratios can be used as a tool to classify AGN in the sub-mm HCN diagram. We produce the classic ionized emission-line ratio diagnostics (the so-called BPT diagrams), using available CARS data from the Multi Unit Spectroscopic Explorer. We then compare the BPT classification with the sub-mm classification made using the dense gas tracers. Where it was possible to complete the analysis we find general agreement between optical and sub-mm classified gas excitation mechanisms. This suggests that AGN can contribute to the excitation of both the low-density gas in the warm ionized medium and the high-density gas in molecular clouds simultaneously, perhaps through X-ray, cosmic ray, or shock heating mechanisms
