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#Astrodon

65 posts55 participants10 posts today
Public
REBOUND Citation Bot

A new paper by Spada has cited REBOUND:
"Dark Comet" 2005 VL1 is Unlikely to be the Lost Soviet-era Probe Venera 2 ui.adsabs.harvard.edu/abs/2025 #nbody #astrodon

ADS · "Dark Comet" 2005 VL<SUB>1</SUB> is Unlikely to be the Lost Soviet-era Probe Venera 2A. Loeb & R. Cloete intriguingly suggest that the near-Earth object 2005 VL<SUB>1</SUB> could be the lost Soviet probe Venera 2. Here I evaluate the plausibility of such a claim against the available data. I have re-determined the orbit of 2005 VL<SUB>1</SUB> (including a non-gravitational acceleration component) using the astrometric observations retrieved from the Minor Planet Center database. By propagating the orbit of 2005 VL<SUB>1</SUB> over the period of the Venera 2 mission, I compare this object's distance from the Earth and from Venus at the times of the probe's launch and flyby with Venus, respectively. My analysis, which takes into account realistic uncertainties on both the orbit of 2005 VL<SUB>1</SUB> and the position of Venera 2, decisively rules out the proposed identification. My approach relies entirely on open-source software and publicly available data, and could represent a viable method to assess similar claims in the future.
Public
franco_vazza

Same initial conditions, same ENZO code evolving a 150Mpc^3 portion of the Universe from z=50 to z=0.
However, the initial σ8 parameter, prescribing the amplitude of the initial matter perturbations within a 8Mpc/h scale, has been changed in regular steps from σ8=0.5 (very low) to σ8=1.0 (very high). "Reality" probably is between 0.8 and 0.7.
This the resulting baryon density distribution in al cases.
#SimulatedUniverses #MAKITRA #Astronomy #Astrodon #Science

Public *
Florian 'floe' Echtler

Hi everyone, I'm currently having an extremely hard time finding reviewers for a paper at @jovi which relates to visualization, simulation, and orbital dynamics. The review version is public at journalovi.org/2024-rein-rebou and the reviews will be public and (optionally) attributed as well. Please ping me if interested, and RT for reach!

www.journalovi.orgReal time, cross platform visualizations with zero dependencies for the N-body package REBOUND
#academia#visualization#space
Public
Daniel Pomarède

#Cosmology

Gigaparsec structures are nowhere to be seen in ΛCDM: an enhanced analysis of LSS in FLAMINGO-10K simulations

by Alexia Lopez @morninglopez and Roger Clowes @rgclowes
arxiv.org/abs/2504.14940

arXiv logo
arXiv.orgGigaparsec structures are nowhere to be seen in $Λ$CDM: an enhanced analysis of LSS in FLAMINGO-10K simulationsRecently, Sawala et al. 2025 claimed to refute the cosmological significance of the Giant Arc based on their analysis of the FLAMINGO-10K simulation data. In our paper here, we highlight several shortcomings of the authors' analysis. We then perform an enhanced analysis on the FLAMINGO-10K simulation data with applications of: the Single-Linkage Hierarchical Clustering (SLHC), the Convex Hull of Member Spheres (CHMS), and the Minimal Spanning Tree (MST) algorithms. Using the full $2.8^3$ Gpc$^3$ FLAMINGO-10K box, with subhaloes at $z=0.7$, and $100$ random realisations (from random subset selections) we find no gigaparsec structures in FLAMINGO-10K, and only a few ultra-large large-scale structures (uLSSs, structures exceeding a maximum pairwise separation of $370$ Mpc). Somewhat surprisingly, we found that the large-scale aspects of the FLAMINGO-10K data could be adequately represented by a Poisson point distribution. The enhanced analysis presented here further supports the remarkable nature of the Giant Arc as a cosmologically-significant structure. Of course, the Giant Arc is also accompanied by a second uLSS, the Big Ring. The analysis presented here builds on the work presented by Sawala et al., but amends the application of their statistical assessments. We do not yet know why there appears to be such a large discrepancy between the FLAMINGO-10K data and the observed LSS in MgII absorbers. Perhaps the results presented here might suggest that the GA, and especially the GA + BR, presents a more direct challenge to $Λ$CDM. In contrast to the conclusion of Sawala et al. that `gigaparsec patterns abound in a $Λ$CDM universe' we find that they are nowhere to be seen.
#GiantArc#BigRing#galaxies
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