Once again, the observed dynamics of galaxies are inconsistent with cold dark matter halos. There are dozens of other completely independent instances of empirical evidence contradicting the LambdaCDM Standard Model of Cosmology. I have faith that eventually this reality will sink into the community of astrophysicists and cosmologists, but I have no idea how long it will take to get there.
Simulations of structure formation in the standard cold dark matter cosmological model quantify the dark matter halos of galaxies. Taking into account dynamical friction between the dark matter halos, we investigate the past orbital dynamical evolution of the Magellanic Clouds in the presence of the Galaxy.
Our calculations are based on a three-body model of rigid Navarro-Frenk-White profiles for the dark matter halos, but were verified in a previous publication by comparison to high-resolution N-body simulations of live self-consistent systems. Under the requirement that the LMC and SMC had an encounter within 20 kpc between 1 and 4 Gyr ago, in order to allow the development of the Magellanic Stream, and using the latest astrometric data, the dynamical evolution of the MW/LMC/SMC system is calculated backwards in time.
With the employment of the genetic algorithm and a Markov-Chain Monte-Carlo method, the present state of this system is unlikely with a probability of <10^-9 (6 sigma complement), because solutions found do not fit into the error bars for the observed plane-of-sky velocity components of the Magellanic Clouds. This implies that orbital solutions that assume dark matter halos according to cosmological structure formation theory to exist around the Magellanic Clouds and the Milky Way are not possible with a confidence of more than 6 sigma.
Wolfgang Oehm and Pavel Kroupa, "The Relevance of Dynamical Friction for the MW/LMC/SMC Triple System" 10 Universe 143 arXiv:2403.17999 (March 26, 2024).
With the employment of the genetic algorithm and a Markov-Chain Monte-Carlo method,
ReplyDeletecomputer simulation
Hum... as a software developer for 40+ years I can say with confidence that there are no bugs in their code. Just features.
ReplyDeletedifferent computer simulation might have different results
ReplyDeletehttps://link.springer.com/article/10.1007/s41115-021-00013-z
ReplyDeleteLarge-scale dark matter simulations
Review Article
Open access
Published: 11 February 2022
Abstract
We review the field of collisionless numerical simulations for the large-scale structure of the Universe. We start by providing the main set of equations solved by these simulations and their connection with General Relativity. We then recap the relevant numerical approaches: discretization of the phase-space distribution (focusing on N-body but including alternatives, e.g., Lagrangian submanifold and Schrödinger–Poisson) and the respective techniques for their time evolution and force calculation (direct summation, mesh techniques, and hierarchical tree methods). We pay attention to the creation of initial conditions and the connection with Lagrangian Perturbation Theory. We then discuss the possible alternatives in terms of the micro-physical properties of dark matter (e.g., neutralinos, warm dark matter, QCD axions, Bose–Einstein condensates, and primordial black holes), and extensions to account for multiple fluids (baryons and neutrinos), primordial non-Gaussianity and modified gravity. We continue by discussing challenges involved in achieving highly accurate predictions. A key aspect of cosmological simulations is the connection to cosmological observables, we discuss various techniques in this regard: structure finding, galaxy formation and baryonic modelling, the creation of emulators and light-cones, and the role of machine learning. We finalise with a recount of state-of-the-art large-scale simulations and conclude with an outlook for the next decade.
Over the last decades, numerical simulations have played a decisive role in establishing and testing this CDM paradigm. Following pioneering work in the 1980s, numerical simulations steadily grew in realism and precision thanks to major advances in algorithms, computational power, and the work of hundreds of scientists. As a result, various competing hypotheses and theories could be compared with observations, guiding further development along the years. Ultimately,
CDM was shown to be quantitatively compatible with virtually all observations of the large-scale structure of the Universe, even for those that involve nonlinear physics and that are inaccessible to any method other than computer simulations (see e.g., Springel et al. 2006; Vogelsberger et al. 2020).
Nowadays, simulations have become the go-to tool in cosmology for a number of tasks: (i) the interpretation of observations in terms of the underlying physics and cosmological parameters; (ii) the testing and aiding of the development of perturbative approaches and analytic models for structure formation; (iii) the production of reliable input (training) data for data-driven approaches and emulators; (iv) the creation of mock universes for current and future large-scale extragalactic cosmological surveys, from which we can quantify statistical and systematic errors; (v) the study of the importance of various aspects of the cosmological model and physical processes, and determining their observability.
Despite the remarkable agreement between simulations and the observed Universe, there are indications that
CDM might not be ultimately the correct theory (Planck Collaboration 2020; Riess et al. 2019; Asgari et al. 2021; DES Collaboration 2021). Future cosmological observations will provide enough data to test competing explanations by probing exceedingly large sub-volumes of the Universe in virtually all electromagnetic wavelengths, and including increasingly fainter objects and smaller structures (e.g. Laureijs et al. 2011; Bonoli et al. 2021; DESI Collaboration 2016; Ivezić et al. 2019; Ade et al. 2019; Merloni et al. 2012). These observations will be able to test the physics of our Universe beyond the standard model: from neutrino masses, over the nature of dark matter and dark energy, to the inflationary mechanism.