4,555 research outputs found
A High-Fidelity Realization of the Euclid Code Comparison -body Simulation with Abacus
We present a high-fidelity realization of the cosmological -body
simulation from the Schneider et al. (2016) code comparison project. The
simulation was performed with our Abacus -body code, which offers high force
accuracy, high performance, and minimal particle integration errors. The
simulation consists of particles in a box,
for a particle mass of with $10\
h^{-1}\mathrm{kpc}z=0<0.3\%k<10\
\mathrm{Mpc}^{-1}h0.01\%$. Simulation snapshots are available at
http://nbody.rc.fas.harvard.edu/public/S2016 .Comment: 13 pages, 8 figures. Minor changes to match MNRAS accepted versio
Reactive Quenching Of Od A (2)Σ(+) By H-2: Translational Energy Distributions For H- And D-Atom Product Channels
The H- and D-atom products from collisional quenching of OD A (2)Sigma(+) by H-2 are characterized through Doppler spectroscopy using two-photon (2 S-2 \u3c-\u3c- 1 S-2) laser-induced fluorescence. Partial deuteration enables separation of the channel forming H + HOD products, which accounts for 75% of reactive quenching events, from the D + H2O product channel. The Doppler profiles, along with those reported previously for other isotopic variants, are transformed into product translational energy distributions using a robust fitting procedure based on discrete velocity basis functions. The product translational energy distribution for the H- atom channel is strongly peaked at low energy (below 0.5 eV) with a long tail extending to the energetic limit. By contrast, the D-atom channel exhibits a small peak at low translational energy with a distinctive secondary peak at higher translational energy (approximately 1.8 eV) before falling off to higher energy. In both cases, most of the available energy flows into internal excitation of the water products. Similar distributions are obtained upon reanalysis of D- and H- atom Doppler profiles, respectively, from reactive quenching of OH A (2)Sigma(+) by D-2. The sum of the translational energy distributions for H- and D- atom channels is remarkably similar to that obtained for OH A (2)Sigma(+) + H-2, where the two channels cannot be distinguished from one another. The product translational energy distributions from reactive quenching are compared with those obtained from a previous experiment performed at higher collision energy, quasiclassical trajectory calculations of the post-quenching dynamics, and a statistical model. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3644763
The Abacus Cosmos: A Suite of Cosmological N-body Simulations
We present a public data release of halo catalogs from a suite of 125
cosmological -body simulations from the Abacus project. The simulations span
40 CDM cosmologies centered on the Planck 2015 cosmology at two mass
resolutions, and , in and
boxes, respectively. The boxes are phase-matched to
suppress sample variance and isolate cosmology dependence. Additional volume is
available via 16 boxes of fixed cosmology and varied phase; a few boxes of
single-parameter excursions from Planck 2015 are also provided. Catalogs
spanning to are available for friends-of-friends and Rockstar
halo finders and include particle subsamples. All data products are available
at https://lgarrison.github.io/AbacusCosmosComment: 13 pages, 9 figures, 3 tables. Additional figures added for mass
resolution convergence tests, and additional redshifts added for existing
tests. Matches ApJS accepted versio
Dynamical tunneling in mushroom billiards
We study the fundamental question of dynamical tunneling in generic
two-dimensional Hamiltonian systems by considering regular-to-chaotic tunneling
rates. Experimentally, we use microwave spectra to investigate a mushroom
billiard with adjustable foot height. Numerically, we obtain tunneling rates
from high precision eigenvalues using the improved method of particular
solutions. Analytically, a prediction is given by extending an approach using a
fictitious integrable system to billiards. In contrast to previous approaches
for billiards, we find agreement with experimental and numerical data without
any free parameter.Comment: 4 pages, 4 figure
Constraining accuracy of the pairwise velocities in -body simulations using scale-free models
We present a continuation of an analysis that aims to quantify resolution of
-body simulations by exploiting large (up to ) simulations of
scale-free cosmologies run using Abacus. Here we focus on radial pairwise
velocities of the matter field, both by direct estimation and through the
cumulative-2PCF (using the pair conservation equation). We find that
convergence at the level of the mean relative pairwise velocity can be
demonstrated over a range of scales, evolving from a few times the grid spacing
at early times to slightly below this scale at late times. We show the analysis
of two different box sizes as well as from averaging results from the smaller
boxes, and compare the power of the two aforementioned estimators in
constraining accuracy at each scale. Down to scales of order of the smoothing
parameter, convergence is obtained at precision, and shows a
behaviour indicating asymptotic stable clustering. We also infer for LCDM
simulations conservative estimates on the evolution of the lower cut-off to
resolution (at and precision) as a function of redshift.Comment: 14 pages, 9 figures, 1 table. Accepted for publication in MNRAS. v2
does NOT overlap with arXiv:2308.0043
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