Portail HAL-PSL
Not a member yet
293219 research outputs found
Sort by
The MeerKLASS UHF On-the-Fly Continuum Survey -- Data Release I
No full textInternational audienceWe present the first public data release (DR1) from the interferometric component of the MeerKAT Large Area Synoptic Survey (MeerKLASS) UHF survey, a legacy program demonstrating a novel on-the-fly (OTF) mapping technique. This release is based on 12 hours of early science observations covering approximately 800 deg of the southern sky. We describe the data processing pipeline developed to calibrate and image these fast-scanning observations, producing high-fidelity continuum images at a central frequency of 816 MHz. The resulting mosaic reaches an RMS sensitivity of 35 Jy beam in its deepest regions, with a typical angular resolution of . In these images, we identify radio sources. We validate the catalogue through cross-matching with external surveys, confirming sub-arcsecond astrometric accuracy and a robust flux density scale. We compute the differential source counts, finding excellent agreement with existing measurements and validating our end-to-end processing. The success of this pilot study serves as a crucial proof of concept for the OTF observing strategy, and the public release of the images and source catalogue provides a valuable resource for a wide range of astrophysical studies. This work paves the way for the full MeerKLASS OTF survey and future large-area survey projects with the SKA
A Rosetta Stone for Wilson Line Defects
No full textInternational audienceIn this paper, we discuss the construction of a map between weak (gauge) and strong (string) coupling degrees of freedom for the supersymmetric Wilson line-defect in the planar N=4 Super-Yang-Mills. By analysing the Partition Functions at zero and infinite coupling, we propose a map from degrees of freedom capturing single- and singlet two-particle states at zero coupling to infinite coupling. This map predicts that the dimension of states in these particular sectors doubles as it goes from zero to infinite coupling. We test this prediction against the non-perturbative spectrum of insertions on the Wilson line obtained using integrability. In addition to already available integrability-based results, we obtain the non-perturbative scaling dimension of the simplest non-trivial operator with transverse spin about the Wilson line, thereby extending the Quantum Spectral Curve construction to such charged sectors
Intrinsic training dynamics of deep neural networks
No full textA fundamental challenge in the theory of deep learning is to understand whether gradient-based training in high-dimensional parameter spaces can be captured by simpler, lower-dimensional structures, leading to so-called implicit bias. As a stepping stone, we study when a gradient flow on a high-dimensional variable implies an intrinsic gradient flow on a lower-dimensional variable , for an architecture-related function . We express a so-called intrinsic dynamic property and show how it is related to the study of conservation laws associated with the factorization . This leads to a simple criterion based on the inclusion of kernels of linear maps which yields a necessary condition for this property to hold. We then apply our theory to general ReLU networks of arbitrary depth and show that, for any initialization, it is possible to rewrite the flow as an intrinsic dynamic in a lower dimension that depends only on and the initialization, when is the so-called path-lifting. In the case of linear networks with the product of weight matrices, so-called balanced initializations are also known to enable such a dimensionality reduction; we generalize this result to a broader class of {\em relaxed balanced} initializations, showing that, in certain configurations, these are the \emph{only} initializations that ensure the intrinsic dynamic property. Finally, for the linear neural ODE associated with the limit of infinitely deep linear networks, with relaxed balanced initialization, we explicitly express the corresponding intrinsic dynamics
Demonstrating Aeolus capability to observe wind-cloud interactions
No full textInternational audienceModel based studies have shown interactions between wind vertical profiles and cloudiness, but few observational studies corroborate them. The unique observations of Aeolus spaceborne Doppler wind lidar can contribute to fill this gap. In this paper, we merged global Aeolus observations of cloud profiles at full horizontal resolution (3 km along orbit track) with co-located profiles of horizontal winds.We first observed wind-cloud interactions at regional scale over the Indian Ocean. Aeolus captures the strengthening of the Tropical Easterly Jet in early June 2020, with wind speeds exceeding 40 m s -1 in its core, and a simultaneous increase of high cloud fraction up to above 30 %, until the decay of the jet during fall.Secondly, we observed wind-cloud interactions at cloud scale (between 3-100 km) in different regions. Over the Indian Ocean as well as over cumulus and stratocumulus dominated regions, we found that the wind shear inside clouds is smaller than the wind shear in the clear sky surrounding the clouds (statistically significant). In addition, we found that the wind speed difference between the cloud and its surrounding clear sky increases with the clear sky wind shear, especially in cumulus (R = -0.94) and stratocumulus (R = -0.87) dominated regions. This study demonstrated that despite its coarse resolution, Aeolus can capture wind perturbations induced by convective motion.</div
L’apogée de la médecine occidentale ancienne : Galien et son héritage
No full textInternational audienc
Words of Aspiration with Advice Granted to Ön Zhenpen Kunga, by Jamyang Khyentse Wangpo
No full textdbon gzhan phan kun dga’ la gnang ba’i zhal gdams smon tshig (B128) Jamyang Khyentse Wangpo Kabum, vol. 1 (ka), 359.1–359.5, Dzongsar, 2014
L’invention de l’Europe par les langues et les cultures (chaire annuelle 2021-2022): [résumé des cours et travaux : 2021-2022]
No full textInternational audienc
S4 modal sequent calculus as intermediate logic and intermediate language
No full textInternational audienceIn this short paper, we advocate for the idea that continuation-based intermediate languages correspondto intermediate logics. The goal of intermediate languages is to serve as a basis for compiler intermediaterepresentations, allowing to represent expressive program transformations for optimisation and compilation,while preserving the properties that make programs compilable efficiently in the first place, such as the“stackability” of continuations. Intermediate logics are logics between intuitionistic and classical logic in termsof provability.Second-class continuations used in CPS-based intermediate languages correspond to a classical modal logicS4 with the added restriction that implications may only return modal types. This indeed corresponds to anintermediate logic, owing to the Gödel-McKinsey-Tarski theorem which states the intuitionistic nature of themodal fragment of S4.We introduce a three-kinded polarised sequent calculus for S4, together with an operational machinemodel that separates a heap from a stack. With this model we study a stackability property for the modalfragment of S4
Abrodictyum polynesicum (Hymenophyllaceae, Polypodiidae), a new fern species for the French Polynesia
No full textInternational audienceThe filmy fern Abrodictyum asae-grayi (Hymenophyllaceae) is thought to be distributed from New Guinea to French Polynesia. However, specimens from the Marquesas Islands and some populations from the Society Islands show clearly erect rhizomes, while the species A. asae-grayi is described as having creeping rhizomes. In-depth examination of the herbarium specimens and phylogenetic analysis demonstrate that the specimens with creeping rhizomes and those with erect rhizomes define two distinct species. The new species, A. polynesicum, endemic to French Polynesia, is discussed and described here