Portail HAL du Collège de France
Not a member yet
22122 research outputs found
Sort by
Monkeys as Keepers and Teachers of Cryptic Celestial Knowledge.The White Gibbon, the Literati Arts and the Secrets of Heaven: Panel "Monkeying Around. Thinking with Monkeys in Pre-modern Chinese culture"
No full textInternational audienceIn Chinese literary tradition as a whole, the gibbons have long enjoyed an exalted statute. Hearing their long and -supposedly- melancholic chant coming from the height of the mountain forests have made the literati believe that gibbons were kindred spirits, natural “zhiyin” 知音 friends of the banished or frustrated scholar. When appearing in wenyan or vernacular narratives, gibbons, especially the figure of the White Gibbon, tend to be able to display a command of some of the literati arts. Though they cannot be said to fully master the four classical arts of “Qin, Chess, Calligraphy and Painting” 棋琴書畫 some of them read, write, sing and play weiqi 圍棋. A further skill, not unrelated to the latter, is their talent in martial arts, especially in swordsmanship. In this paper, we explore first the long-lasting myth which links monkeys to celestial books or tianshu 天書, written in cryptic characters and containing the secrets of warfare or alchemical arts. We analyse the role of monkeys towards those heavenly archives, and especially the way they are both their keepers against disclosure and their transmitters/teachers to worthy -- or sometimes not so worthy-- humans, and how they are mediating between those humans and the female immortals often linked to those texts. Then, we turn towards the legend of the chess-playing gibbon, where a simian companion of a holy Buddhist monk shows such a command of the strategic game that his clerical master has to make him leave the world by dying, lest some inner mechanism of the “former heaven” xiantian 先天would be leaked on the chess board. Our last example display a gibbon singing so beautifully, in a human voice, that the evil fox-spirit Daji, enraptured, is obliged to reveal her true nature, and escapes narrowly being caught. Though the singing or chess-playing gibbons lack the capacity of human language that the tianshu-keeping gibbons are endowed with, the « speechless » magical white gibbons play nevertheless a role very much similar to their tianshu-legends counterparts: transmitting esoteric secrets. What they only lack is human-like autonomy, and it’s probably why they are shown mentored by humans, or even said to be eventually lost because « being only animals
Ten demystified folios from Ablai-kit
No full textInternational audienceThe authors discuss ten folios from Ablai-kit that contain texts typically localized in the Tengyur. A closer analysis, however, reveals that this was not the case with these folios, dismantling the initial hypothesis that this part of the Tibetan Buddhist canon might have been kept along with the Kangyur in the Oirat monastery. Nevertheless, the analysis does add further support to the argument that Ablai-kit possessed a unique version of the Kangyur that has no parallels with any other known versions. The appendix to the article contain the full list of 250 folios of the Ablai-kit Kangyur so far identified in twelve Russian and Western European collections
The Persistence of the Tea House as a Japanese Dwelling’s Ideal. From Its Establishment as a Model to Contemporary Inquiry
No full textInternational audienc
Search for gravitational-lensing signatures in the full third observing run of the LIGO-Virgo network
No full textInternational audienceGravitational lensing by massive objects along the line of sight to the source causes distortions of gravitational wave-signals; such distortions may reveal information about fundamental physics, cosmology and astrophysics. In this work, we have extended the search for lensing signatures to all binary black hole events from the third observing run of the LIGO--Virgo network. We search for repeated signals from strong lensing by 1) performing targeted searches for subthreshold signals, 2) calculating the degree of overlap amongst the intrinsic parameters and sky location of pairs of signals, 3) comparing the similarities of the spectrograms amongst pairs of signals, and 4) performing dual-signal Bayesian analysis that takes into account selection effects and astrophysical knowledge. We also search for distortions to the gravitational waveform caused by 1) frequency-independent phase shifts in strongly lensed images, and 2) frequency-dependent modulation of the amplitude and phase due to point masses. None of these searches yields significant evidence for lensing. Finally, we use the non-detection of gravitational-wave lensing to constrain the lensing rate based on the latest merger-rate estimates and the fraction of dark matter composed of compact objects
La Quintessence des Joyaux, Instructions sur les Principes du Franchissement du Pic (Thod rgal gyi don khrid nor bu’i snying po)
No full textThe Solar System could have formed in a low-viscosity disc: A dynamical study from giant planet migration to the Nice model
No full textInternational audienceContext. In the context of low-viscosity protoplanetary discs (PPDs), the formation scenarios of the Solar System should be revisited. In particular, the Jupiter-Saturn pair has been shown to lock in the 2:1 mean motion resonance while migrating generally inwards, making the Grand Tack scenario impossible.Aims. We explore what resonant chains of multiple giant planets can form in a low-viscosity disc, and whether these configurations can evolve into forming the Solar System in the post gas disc phase.Methods. We used hydrodynamical simulations with the code FARGOCA to study the migration of the giant planets in a disc with viscosity parameter of α = 10−4. After a transition phase to a gas-less configuration, we studied the stability of the obtained resonant chains through their interactions with a disc of leftover planetesimals by performing N-body simulations using rebound.Results. The gaps opened by giant planets are wider and deeper for lower viscosity, reducing the damping effect of the disc. Thus, when planets enter a resonance, the resonant angle remains closer to circulation, making the chain weaker. Exploring numerous configurations, we found five stable resonant chains of four or five planets. In a thin (cold) PPD, the four giant planets revert their migration and migrate outwards. After disc dispersal, under the influence of a belt of planetesimals, some resonant chains undergo an instability phase while others migrate smoothly over a billion years. For three of our resonant chains, about ~1% of the final configurations pass the four criteria to fit the Solar System. The most successful runs are obtained for systems formed in a cold PPD with a massive planetesimal disc.Conclusions. This work provides a fully consistent study of the dynamical history of the Solar System’s giant planets, from the protoplanetary disc phase up to the giant planet instability. Although building resonant configurations is difficult in low-viscosity discs, we find it possible to reproduce the Solar System from a cold, low-viscosity protoplanetary disc
Interlaboratory Comparison of Branched GDGT Temperature and pH Proxies Using Soils and Lipid Extracts
No full textInternational audienceRatios of glycerol dialkyl glycerol tetraethers (GDGT), which are membrane lipids of bacteria and archaea, are at the base of several paleoenvironmental proxies. They are frequently applied to soils as well as lake‐ and marine sediments to generate records of past temperature and soil pH. To derive meaningful environmental information from these reconstructions, high analytical reproducibility is required. Based on submitted results by 39 laboratories from across the world, which employ a diverse range of analytical and quantification methods, we explored the reproducibility of brGDGT‐based proxies (MBT′, IR, and #rings) measured on four soil samples and four soil lipid extracts. Correct identification and integration of 5‐ and 6‐methyl brGDGTs is a prerequisite for the robust calculation of proxy values, but this can be challenging as indicated by the large inter‐interlaboratory variation. The exclusion of statistical outliers improves the reproducibility, where the remaining uncertainty translates into a temperature offset from median proxy values of 0.3–0.9°C and a pH offset of 0.05–0.3. There is no apparent systematic impact of the extraction method and sample preparation steps on the brGDGT ratios. Although reported GDGT concentrations are generally consistent within laboratories, they vary greatly between laboratories. This large variability in brGDGT quantification may relate to variations in ionization efficiency or specific mass spectrometer settings possibly impacting the response of brGDGTs masses relative to that of the internal standard used. While ratio values of GDGT are generally comparable, quantities can currently not be compared between laboratories
Non-minimal couplings to -gauge fields and asymptotic symmetries
No full textInternational audienceWe analyse the asymptotic symmetries of electromagnetism non-minimally coupled to scalar fields, with non-minimal couplings of the Fermi type that occur in extended supergravity models. Our study is carried out at spatial infinity where minimal and non-minimal couplings exhibit very different asymptotic properties: while the former generically cannot be neglected at infinity, the latter can. Electromagnetic non-minimal couplings are in that respect similar to gravitational minimal couplings, which are also asymptotically subdominant. Because the non-minimally interacting model is asymptotic to the free one, its asymptotic symmetries are the same as the ones of the free theory, i.e., described by angle-dependent gauge transformations. We also analyse the duality symmetry and show that it is broken to its compact subgroup by the asymptotic conditions. Finally, we consider logarithmic gauge transformations and use them to simplify the symmetry algebra
Spectral signatures of non-trivial topology in a superconducting circuit
No full textInternational audienceTopology, like symmetry, is a fundamental concept in understanding general properties of physical systems. In condensed matter systems, non-trivial topology may manifest itself as singular features in the energy spectrum or the quantization of observable quantities such as electrical conductance and magnetic flux. Using microwave spectroscopy, we show that a superconducting circuit with three Josephson tunnel junctions in parallel can possess energy degeneracies indicative of non-trivial topology. We identify three topological invariants, one of which is related to a hidden quantum mechanical supersymmetry. Depending on fabrication parameters, devices are gapless or not, and fall on a simple phase diagram which is shown to be robust to perturbations including junction imperfections, asymmetry, and inductance. Josephson tunnel junction circuits, which are readily fabricated with conventional microlithography techniques, allow access to a wide range of topological systems which have no condensed matter analog. Notable spectral features of these circuits, such as degeneracies and flat bands, may be leveraged for quantum information applications, whereas quantized transport properties could be useful for metrology applications