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Multi-model physics informed neural networks to the shallow water equations for cosine bell advection
No full textSolving the shallow water equations is essential in science and engineering for understanding and predicting geophysical phenomena such as atmospheric and oceanic flows. Physics-informed machine learning has emerged as a powerful alternative to traditional numerical methods, avoiding the complexities of grid generation and enabling mesh-free solutions to partial differential equations. In this study, we apply a sequential multi-model approach within a time-decomposed framework to solve the shallow water equations on a rotating sphere, in the context of meteorological applications. We employed advanced physics-informed neural networks integrated with deep learning, using diverse network architectures to conduct a detailed analysis of cosine bell advection across multiple orientations on the Earth. The results demonstrate high predictive accuracy, underscoring the method’s transformative potential for geophysical fluid dynamics. We also implemented a finite difference upwind scheme and a fully data-driven deep neural network to supplement the validation process and comparative analysis. Additionally, we perform a sensitivity analysis to examine the influence of physics-informed error terms on the training dynamics of the networks.</p
Cultivating green growth through innovative city pilot policies:Evidence from China
No full textThis study utilises panel data encompassing 282 prefectural-level cities in China spanning the years 2007 to 2019. Its primary objectives are to assess the direct and indirect consequences of the National Innovative City Pilot Policy (NICPP) on Green Total Factor Productivity (GTFP) through the application of the Propensity Score Matching (PSM) and Difference-in-Difference (DID) models. Subsequently, the research delves into whether NICPP can enhance the GTFP of cities by means of fiscal investments in science and technology, the degree of green innovations, and the level of financial development. Additionally, robustness tests and heterogeneity analyses are conducted to strengthen the validity of the findings. The results indicate that NICPP positively influences the GTFP of cities, primarily via these three mechanisms.</p
Digitalisering af planer i Danmark – mellem afrapportering og støtte til planlægning
No full textProjektet DIGIPLAN har undersøgt, hvordan digitale planer og plandata er repræsenteret, og hvordan plandata bruges i og påvirker planlægningspraksis. Dette er gjort via en overordnet analyse af digitale planer i 15 europæiske lande og 6 dybdegående casestudier, herunder i Danmark
Petrologic and Thermodynamic Constraints on the Petrogenesis of the Fiskenæsset Anorthosite Complex, SW Greenland:An Anhydrous Model for Archean Anorthosites
No full textHere we present a new study of the petrology, geochemistry and thermodynamic modeling of the ∼ 2.97 Ga Mesoarchean Fiskenæsset Anorthosite Complex (FAC) in southern West Greenland. Our results provide new constraints on the parental magma and the crystallization history of the complex with implications for the petrogenesis and the geodynamic setting of Archean anorthosites. Detailed logging, petrography and mineral chemistry of an ∼ 80-m-long drill core intersecting anorthosite at Majorqap Qâva show that the rock is nearly monomineralic and has homogenous plagioclase compositions averaging An87 ± 1 throughout the drill core. Based on textural relations, the composition of mineral inclusions and thermodynamic modeling, we argue that the abundant amphiboles are solely metamorphic in origin and formed by the hydration and recrystallization of primary clinopyroxene. Thermodynamic modeling using Rhyolite-MELTS of various proposed parental magmas shows that the petrogenesis of the FAC rocks and similar high-An anorthosite can best be explained by crystallization of an anhydrous high-Al tholeiitic parental melt at shallow pressure (≤3 kbar), which results in early plagioclase saturation with a short interval of essentially plagioclase-only crystallization. Formation of such voluminous and homogenous anorthosites has further required frequent magma replenishment and physical sorting of the cumulates. Flotation of buoyant plagioclase is possible under anhydrous conditions only, and a process supported by previous studies of the FAC, the occurrence of snow-flake and megacrystic rocks (some with negative Eu anomalies), and the large variation in Mg# of high-An anorthosites. The modeling results further demonstrate that the relatively evolved chromites (Cr# 46-67 and Cr/Fe2+ of 1-1.2) associated with the anorthosites cannot have co-crystallized with the high-An plagioclase. Instead, we propose that the anorthositic-chromitiferous rocks formed via either melt rock dissolution and replacement reactions in noritic-gabbronoritic cumulates, the injection of chromitite slurries into anorthosite mush or injection of an anorthosite slurry into chromitite. Alternatively, the chromitite compositions of the FAC experienced significant modification during metamorphism. The combined results of this study provide a genetic link between the FAC and tholeiites of the spatially associated Bjørnesund Supracrustal Belt, representing a shallow, dry and open subvolcanic system. We propose a new petrogenetic model in which the high-Al parental magma of the FAC derived from a more primitive picritic precursor, which ponded and assimilated mafic Archean crust in the lower to middle crust prior to final emplacement as plagioclase supersaturated melts in the upper crust. The emplacement of high-Al tholeiites resulted in massive anorthosite formation and feed the Bjørnesund Supracrustal Belt with melts. In contradiction with previous research, we argue against a hydrous subduction zone setting of the FAC and Fiskenæsset region around 3 Ga, suggesting simpler alternatively non-uniformitarian settings (e.g. ocean-plateau, rift, stagnant-lid). A similar model may apply for other Archean anorthosites, involving unique petrogenetic conditions of the Archean, facilitating high-degree melting of dry mantle, magmatic ponding, assimilation of mafic crust and generation of high-Al tholeiites.</p
Quadratic Quasinormal Mode Dependence on Linear Mode Parity
No full textQuasinormal modes (QNMs) uniquely describe the dominant piece of the gravitational-wave ringdown of postmerger black holes. While the linear QNM regime has been extensively studied, recent work has highlighted the importance of second-perturbative-order, quadratic QNMs (QQNMs) arising from the nonlinear coupling of linear QNMs. Previous attempts to quantify the magnitude of these QQNMs have shown discrepant results. Using a new hyperboloidal framework, we resolve the discrepancy by showing that the QQNM/QNM ratio is a function not only of the black hole parameters but also of the ratio between even- and odd-parity linear QNMs: the ratio QQNM/QNM depends on what created the ringing black hole, but only through this ratio of even- to odd-parity linear perturbations.</p
The Late Maastrichtian Rørdal Member (Denmark):a remarkable window of climatic, environmental and biotic changes at orbital timescales
No full textThe Late Maastrichtian Rørdal Member of the Møns Klint Formation is a remarkable lithological unit of the Danish Basin, characterized by chalk–marl cyclicity, standing out from pure Maastrichtian white chalk within the Chalk Group. A cyclostratigraphic analysis across this unit suggests a control by orbital precession and a strong amplitude modulation of the precession by the 405 kyr eccentricity cycle. Oxygen isotope data from bulk carbonate, benthic foraminifera and brachiopods indicate a prominent cooling commencing at the base of the unit, with maximum cooling aligned with a 405 kyr amplitude modulation maximum. This unit thus represents a rare example of a climatic cooling associated with a 405 kyr insolation maximum. However, geochemical and calcareous nannofossil data support lower productivity levels across the unit, in contradiction to an expected ocean fertilization accompanying enhanced continental weathering as the source of the clay material. An alternative model of deposition for this lithological unit is thus proposed via dense water cascading favoured by a sea-level low, subsequent restriction of the Chalk Sea and associated gravity currents responsible for the resuspension of fine clastic deposits from the margins of the Baltic Shield.</p
Ringdown nonlinearities in the eikonal regime
No full textThe eikonal limit of black hole quasinormal modes (the large multipole limit ≫1) can be realized geometrically as a next-to-leading order solution to the geometric optics approximation, and also as linear fluctuations about the Penrose limit plane wave adapted to the light ring. Extending this interpretation beyond the linear order in perturbation theory requires a robust understanding of quadratic quasinormal modes for large values of . We analyze numerically the relative excitation of quadratic to linear quasinormal modes of Schwarzschild black holes, with two independent methods. Our results suggest that the ratio of quadratic to linear amplitudes for the ×→2 channel converges towards a finite value for large , in sharp contrast with a recent proposal inspired by the Penrose limit perspective. On the other hand, the 2×→+2 channel seems to have a linearly growing ratio. Nevertheless, we show that there is no breakdown of black hole perturbation theory for physically realistic initial data.</p
Two-photon correlations and Hong-Ou-Mandel visibility from an imperfect single-photon source
No full textCalibrating photomultiplier tubes beyond their performance envelope
No full textLeading-edge research is done with blunt instruments when no instrument yet exists for an alluring investigation beyond the edge. Ambitious users then push the envelope of existing instruments to venture beyond the edge. Thus, here we calibrate photomultiplier tubes (PMTs) well beyond their performance envelope in order to achieve super-localization with an unmodified commercial two-photon fluorescence excitation microscope (2PM); deep in the scattering tissue of the mouse brain in vivo; and fast enough to enable nanoscale tracking of particles, capillary walls, and red blood cells [Kutuzov, Lauritzen, and Flyvbjerg (unpublished) (2025)]. This PMT-calibration comprises steps of generic interest: (i) characterizations of a time-dependent bias in the dark noise; (ii) elimination of this bias with a quick-and-noisy protocol; (iii) elimination of this bias with a noiseless protocol when the bias is periodic; (iv) characterization of residual dark output; (v) mathematical characterization of PMT-output for single-photoelectron input; and (vi) mathematical characterization of PMT-output for a given expected number of photoelectrons in input. The extreme attention to details in this calibration of the instrument and in our characterization of its output is necessary in order to squeeze optimal localization accuracy and precision out of quickly recorded—and hence faint—images that are contaminated with irrelevant details about the instrument’s design because we use the instrument beyond its performance envelope.Leading-edge research is done with blunt instruments when no instrument yet exists for an alluring investigation beyond the edge. Ambitious users then push the envelope of existing instruments to venture beyond the edge. Thus, here we calibrate photomultiplier tubes (PMTs) well beyond their performance envelope in order to achieve super-localization with an unmodified commercial two-photon fluorescence excitation microscope (2PM); deep in the scattering tissue of the mouse brain in vivo; and fast enough to enable nanoscale tracking of particles, capillary walls, and red blood cells [Kutuzov, Lauritzen, and Flyvbjerg (unpublished) (2025)]. This PMT-calibration comprises steps of generic interest: (i) characterizations of a time-dependent bias in the dark noise; (ii) elimination of this bias with a quick-and-noisy protocol; (iii) elimination of this bias with a noiseless protocol when the bias is periodic; (iv) characterization of residual dark output; (v) mathematical characterization of PMT-output for single-photoelectron input; and (vi) mathematical characterization of PMT-output for a given expected number of photoelectrons in input. The extreme attention to details in this calibration of the instrument and in our characterization of its output is necessary in order to squeeze optimal localization accuracy and precision out of quickly recorded—and hence faint—images that are contaminated with irrelevant details about the instrument’s design because we use the instrument beyond its performance envelope.</p