arXiv subjects

Adam Clark

Publications and source records attributed to Adam Clark.

7 recordsLinked to original sources

arXiv2026

Binary black hole scattering with generic spins

In this Letter, we confront high-order post-Minkowskian (PM) predictions for generic-spin black-hole scattering with numerical-relativity (NR) simulations for the first time, targeting improvements for eccentric and precessing waveform modelling. We extract azimuthal and polar scattering angles from NR and relate them to the PM spin-kick observable. We introduce asymptotic Euler angles for unbound motion and derive their geometric relation to the scattering angles. Notably, NR exposes a strong-field precessional turning-point structure, including a polar-angle sign change absent in the perturbative PM results.

gr-qc↗

arXiv2026

HiLiftAeroML: High-Fidelity Computational Fluid Dynamics Dataset for High-Lift Aircraft Aerodynamics

This paper describes the first-ever open-source high-fidelity CFD dataset of a high-lift aircraft for the purpose of AI surrogate model development. The dataset is composed of 1800 samples, arising from 180 geometry variants and 10 angles of attack for the high-lift NASA Common Research Model (CRM) geometry, used within the AIAA High-Lift Prediction Workshop series. One of the novelties of this dataset is the use of a GPU-accelerated high-fidelity explicit, wall-modeled LES approach for each simulation, using solution-adapted grids between 300M and 500M cells. This ensures the greatest possible accuracy given known challenges in steady-state RANS approaches for these portions of the flight envelope. The entire dataset (geometries, time-averaged volume and surface variables and integral forces) are available, free of charge with a permissive open-source license (CC-BY-4.0). By making this data publicly available, we aim to accelerate the research and development of AI surrogate modeling within the aerospace industry.

physics.flu-dyn↗

arXiv2025

Strong Field Scattering of Two Black Holes: Exploring Gauge Flexibility

Recent advances in post-Minkowskian (PM) gravity provide new avenues for the high precision modeling of compact binaries. In conjunction with the effective one body (EOB) formalism, highly accurate PM informed models of binary black holes on scattering trajectories have emerged. Several complementary approaches currently exist, in particular the SEOB-PM model, the $w$_{\rm EOB} framework and the recent Lagrange-EOB (LEOB) approach. These models incorporate PM results in fundamentally different ways, employing distinct resummation schemes and gauge choices. Notably, both SEOB-PM and LEOB have been used to compute gravitational waves of bound systems, showing excellent agreement with numerical relativity (NR). The essential component to all of the models is the EOB mass-shell condition describing the dynamics of the two-body spacetime. In this work we will investigate how this mass-shell condition is constructed, paying particular attention to the impact of gauge choices and how they interact with different resummation schemes, showing that there is a strong dependence on both coordinate choice and EOB gauge. For the region of parameter space considered, we find that the best performing gauges coincide with the choices made in SEOB-PM and $w$_{\rm EOB}, with other choices exhibiting worse performance. The case of spinning black holes is also considered, where the current techniques for spinning EOB-PM are reviewed and compared. We also introduce a new gauge based upon the centrifugal radius, which improves upon previous models, particularly for large and negative spins. This offers a promising avenue for further resummation of spin information within the EOB-PM framework.

gr-qc↗

arXiv2019

Measurement of $^{34}$S($^{3}$He,p)$^{36}$Cl cross sections for early solar system nuclide enrichment

Isotopic studies of meteorites have provided ample evidence for the presence of short-lived radionuclides (SLRs) with half-lives of less than 100 Myr at the time of the formation of the solar system. The origins of all known SLRs is heavily debated and remains uncertain, but the plausible scenarios can be broadly separated into either local production or outside injection of stellar nucleosynthesis products. The SLR production models are limited in part by reliance on nuclear theory for modeling reactions that lack experimental measurements. Reducing uncertainty on critical reaction cross sections can both enable more precise predictions and provide constraints on physical processes and environments in the early solar system. This goal led to the start of a campaign for measuring production cross sections for the SLR $^{36}$Cl, where Bowers et al. found higher cross sections for the ${}^{33}$S($\alpha$,p)$^{36}$Cl reaction than were predicted by Hauser-Feshbach based nuclear reaction codes TALYS and NON-SMOKER. This prompted re-measurement of the reaction at five new energies within the energy range originally studied, resulting in data slightly above but in agreement with TALYS. Following this, efforts began to measure cross sections for the next most significant reaction for $^{36}$Cl production, $^{34}$S($^{3}$He,p)$^{36}$Cl. Activations were performed to produce 9 samples between 1.11 MeV/nucleon and 2.36 MeV/nucleon. These samples were subsequently measured with accelerator mass spectrometry at two labs. The resulting data suggest a sharper-than-expected rise in cross sections with energy, with peak cross sections up to 30\% higher than predictions from TALYS.

nucl-ex↗

arXiv2017

Re-measurement of the ${}^{33}$S($\alpha$,p)${}^{36}$Cl cross section for Early solar system enrichment

Short-lived radionuclides (SLRs) with half-lives less than 100 Myr are known to have existed around the time of the formation of the solar system around 4.5 billion years ago. Understanding the production sources for SLRs is important for improving our understanding of processes taking place just after solar system formation as well as their timescales. Early solar system models rely heavily on calculations from nuclear theory due to a lack of experimental data for the nuclear reactions taking place. In 2013, Bowers et al. measured ${}^{36}$Cl production cross sections via the ${}^{33}$S($\alpha$,p) reaction and reported cross sections that were systematically higher than predicted by Hauser-Feshbach codes. Soon after, a paper by Peter Mohr highlighted the challenges the new data would pose to current nuclear theory if verified. The ${}^{33}$S($\alpha$,p)${}^{36}$Cl reaction was re-measured at 5 energies between 0.78 MeV/A and 1.52 MeV/A, in the same range as measured by Bowers et al., and found systematically lower cross sections than originally reported, with the new results in good agreement with the Hauser-Feshbach code TALYS. Loss of Cl carrier in chemical extraction and errors in determination of reaction energy ranges are both possible explanations for artificially inflated cross sections measured in the previous work.

nucl-ex↗

arXiv2016

Activity measurement of 60Fe through the decay of 60mCo and confirmation of its half-life

The half-life of the neutron-rich nuclide, {\fesixty} has been in dispute in recent years. A measurement in 2009 published a value of $(2.62 \pm 0.04)\times10^{6}$ years, almost twice that of the previously accepted value from 1984 of $(1.49 \pm 0.27)\times10^{6}$ years. This longer half-life was confirmed in 2015 by a second measurement, resulting in a value of $(2.50 \pm 0.12)\times10^{6}$ years. All three half-life measurements used the grow-in of the $\gamma$-ray lines in {\nisixty} from the decay of the ground state of $^{60}\text{Co}$ (t$_{1/2}$=5.27 years) to determine the activity of a sample with a known number of {\fesixty} atoms. In contrast, the work presented here measured the {\fesixty} activity directly via the 58.6 keV $\gamma$-ray line from the short-lived isomeric state of $^{60}\text{Co}$ (t$_{1/2}$=10.5 minutes), thus being independent of any possible contamination from long-lived $^{60\text{g}}\text{Co}$. A fraction of the material from the 2015 experiment with a known number of {\fesixty} atoms was used for the activity measurement, resulting in a half-life value of $(2.72 \pm 0.16)\times10^{6}$ years, confirming again the longer half-life. In addition, {\fesixty}/{\fe} isotopic ratios of samples with two different dilutions of this material were measured with Accelerator Mass Spectrometry (AMS) to determine the number of {\fesixty} atoms. Combining this with our activity measurement resulted in a half-life value of $(2.69 \pm 0.28)\times 10^{6}$ years, again agreeing with the longer half-life.

nucl-ex↗

arXiv2003

Construction of bosonic string theory on infinitely curved Anti-de Sitter space

Free scalar field theory in the sector with a large number of particles can be interpreted as bosonic string theory on anti-de Sitter space of vanishing radius. Different ways of writing the field theory Hamiltonian translate to different ways of reparametrizing the world-sheet sigma coordinate. Adding a mass term in the field theory corresponds to cutting off the warped AdS direction, with cut-off inversely proportional to the mass. The string theory has neither tachyon, nor critical dimension.

hep-th↗