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Constraints on gravitational waves from the 2024 Vela pulsar glitch
No full textInternational audienceAmong known neutron stars, the Vela pulsar is one of the best targets for gravitational-wave searches. It is also one of the most prolific in terms of glitches, sudden frequency changes in a pulsar's rotation. Such glitches could cause a variety of transient gravitational-wave signals. Here we search for signals associated with a Vela glitch on 29 April 2024 in data of the two LIGO detectors from the fourth LIGO--Virgo--KAGRA observing run. We search both for seconds-scale burst-like emission, primarily from fundamental (f-)mode oscillations, and for longer quasi-monochromatic transients up to four months in duration, primarily from quasi-static quadrupolar deformations. We find no significant detection candidates, but for the first time we set direct observational upper limits on gravitational strain amplitude that are stricter than what can be indirectly inferred from the overall glitch energy scale. We discuss the short- and long-duration observational constraints in the context of specific emission models. These results demonstrate the potential of gravitational-wave probes of glitching pulsars as detector sensitivity continues to improve
Celestial Symmetries and Subleading Phase Space of Null Hypersurfaces
No full textInternational audiencePursuing our analysis of [1], we study the gravitational solution space around a null hypersurface in the bulk of spacetime, such as a black hole or a cosmological horizon. We discuss the corresponding characteristic initial value problem both in the metric and Newman-Penrose formalisms, and establish an explicit dictionary between the two. This allows us to identify Weyl-covariant structures in the solution space, including hierarchies of recursion relations encoding the flux-balance laws. We then establish a correspondence between the gravitational phase space at null infinity and the subleading phase space around the null hypersurface at finite distance. This connection is naturally formulated within the Newman-Penrose formalism by performing a partially off-shell conformal compactification and identifying the analogue of the Ashtekar-Streubel symplectic structure in the radial expansion near the null hypersurface. Using this framework, we identify the celestial symmetries in the subleading phase space at finite distance by constructing their canonical generators and imposing self-duality conditions. This allows us to define a notion of covariant radiation, whose absence gives rise to an infinite tower of conserved charges, revealing physical quantities relevant to observers near black hole or cosmological horizons. As a concrete illustration, we consider the case of the self-dual Taub-NUT black hole
Verified Persistent Catenable Deques
No full textInternational audienceThe simple persistent catenable deques invented by Kaplan, Okasaki, and Tarjan (2000) support insertion and extraction at either end and concatenation. They have mutable internal state and rely on a restricted form of mutation; yet they are persistent, that is, they appear to be immutable. Using Iris, we verify that they are correct in sequential and concurrent usage scenarios. Using Iris with time credits, we verify that, provided concurrent accesses are forbidden, every operation has amortized time complexity O(1). This requires repairing a certain mysterious condition in Kaplan, Okasaki, and Tarjan's description
: The Unspoken at Work in Selected Literary Testimonies from Fukushima
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Faire taire l’intertextualité ? La réception de l’œuvre d’Agapios Landos dans la controverse eucharistique autour de la Perpétuité de la foi (1669)
No full textInternational audienceThis article examines the reception of the Salut des pécheurs by Agapios Landos in the first volume of the Perpétuité de la foi. Having identified the collection of works consulted by French theologians, we analyse the construction of the image of Agapios as an archetype of an Orthodox Athonite, affirming faith in the real presence of Christ in the Eucharist, and the need for “good dispositions” in order to receive communion worthily. Nevertheless, Agapios’s work is strongly inspired by Catholic sources, and this interconfessional substratum is deliberately hidden by the author himself and by French theologians, while the overconfessionalisation of the image of Agapios, by both these parties, relates in each case to the intraconfessional issues specific to Greek Orthodoxy and French Catholicism.Nous interrogeons la réception du Salut des pécheurs d’Agapios Landos dans le premier tome de la Perpétuité de la foi. Ayant identifié la collection des ouvrages consultée par les Messieurs de Port-Royal, nous y analysons la construction de l’image d’Agapios devenant un archétype d’athonite orthodoxe témoin de la foi dans la présence réelle et dans la nécessité des « bonnes dispositions » pour communier dignement. En revanche, l’ouvrage d’Agapios est fortement inspiré par des sources catholiques, et ce substrat interconfessionnel est caché délibérément par l’auteur lui-même et par les théologiens français, tandis que la surconfessionnalisation de l’image d’Agapios se fait dans les deux cas par rapport aux enjeux intraconfessionnels propres à l’orthodoxie grecque et au catholicisme français
Appendix 1: Pönsé Khyungö Tsal and his identification with Rigdzin Gödem
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Impact of active galactic nuclei and nuclear star formation on the ISM turbulence of galaxies: Insights from JWST/MIRI spectroscopy
No full textInternational audienceActive galactic nuclei (AGNs), star formation (SF), and galaxy interactions can drive turbulence in the gas of the interstellar medium (ISM), which, in turn, plays a role in SF taking place within galaxies. The impact on molecular gas is of particular importance, as it serves as the primary fuel for SF. Our goal is to investigate the origin of turbulence and the emission of molecular gas, as well as low-and-intermediate-ionisation gas, in the inner few kpc of both AGN hosts and star-forming galaxies (SFGs). We used archival JWST MIRI/MRS observations of a sample consisting of 54 galaxies at z < 0.1. We present flux measurements for the H2 S(5)λ6.9091 μm, [ArII]λ6.9853 μm, [FeII]λ5.3403 μm, and [ArIII]λ8.9914 μm emission lines along with velocity dispersion estimated by the W80 parameter. For galaxies with coronal line emission, we included measurements of the [MgV]λ5.6098 μm line. We compared the line ratios to photoionisation and shock models to explore the origin of the gas emission. AGNs exhibit broader emission lines than SFGs, with the largest velocity dispersions observed in radio-strong (RS) AGNs. The H2 gas is less turbulent compared to ionised gas, while coronal gas presents higher velocity dispersions. The W80 values for the ionised gas show a decrease when going from the nucleus out to radii of approximately 0.5–1 kpc, followed by an outward increase up to 2–3 kpc. In contrast, the H2 line widths generally display increasing profiles with distance from the center. Correlations between the W80 parameter and line ratios such as H2S(5)/[Ar II] and [Fe II]/[Ar II] indicate that the most turbulent gas is associated with shocks, enhancing H2 and [Fe II] emissions. Based on the observed line ratios and velocity dispersions, the [FeII] emission is consistent with predictions of fast shock models, while the H2 emission is likely associated with molecules formed in the post-shock region. We speculate that these shocked gas regions are produced by AGN outflows and jet-cloud interactions in AGN-dominated sources; whereas in SFGs, they might be created through stellar winds and mergers. This shock-induced gas heating may be an important mechanism of AGN (or stellar) feedback, preventing the gas from cooling and forming new stars.Key words: galaxies: active / galaxies: evolution / galaxies: ISM / galaxies: kinematics and dynamic