Dark matter and turbulence: APS 75th Annual Meeting of the Division of Fluid Dynamics 2022 Nov Indianpolis
Creators: name: Zhijie (Jay) Xu
Publisher: name: Zenodo
Year: 2022
Subjects: cosmology
dark matter
turbulence
astronomy
astrophysics
N body
two-thrids law
three-fourth law
mass cascade
energy cascade
dark matter particle mass
dark matter particle size
dark matter particle property

description: How can the fluid mechanics help us understand the dark matter mystery - the biggest quest of contemporary astrophysics? Dark matter can be characterized by the mass and size of its smallest constituents, which are challenging to be directly probed and detected. After years of null results in the search for thermal WIMPs, a different prospective might be required beyond the standard WIMP paradigm. We present a new approach to estimate the dark matter particle mass, size, density, and many other relevant properties based on the nature of flow of dark matter. A comparison with hydrodynamic turbulence is presented to reveal the unique features of self-gravitating collisionless dark matter flow, i.e. an inverse mass and energy cascade from small to large scales with a scale-independent rate of energy cascade ε<sub>u</sub>=-4.6x10<sup>-7</sup>m<sup>2</sup>/s<sup>3</sup>. For the simplest case with only gravitational interaction involved and in the absence of viscosity in flow, the energy cascade leads to a two-thirds law for pairwise velocity that can be extended down to the smallest scale, where quantum effects become important. Combining the rate of energy cascade <strong>ε<sub>u</sub></strong>, the Planck constant <strong>h</strong>, and the gravitational constant <strong>G</strong> on the smallest scale, the mass of dark matter particles is found to be around 0.9x10<sup>12</sup>GeV with a size around 3x10<sup>-13</sup>m. Since the mass m<sub>X</sub> is only weakly dependent on ε<sub>u</sub> as <strong>m<sub>X</sub></strong> <strong>∝</strong><strong> (-ε<sub>u</sub>h<sup>5</sup>/G<sup>4</sup>)<sup>1/9</sup></strong>, the estimation of m<sub>X</sub> should be pretty robust for a wide range of possible values of ε<sub>u</sub>. If gravity is the only interaction and dark matter is fully collisionless, mass of around 10<sup>12</sup>GeV is required to produce the given rate of energy cascade ε<sub>u</sub>. This strongly suggests a heavy dark matter scenario with a mass much greater than the standard thermal WIMPs. Applications of cascade and statistical theory for dark matter and bulge-SMBH evolution: Dark matter particle mass ,size, and properties from energy cascade in dark matter flow: 1) arxiv 2) zenodo slides Origin of MOND acceleration &amp; deep-MOND from acceleration fluctuation &amp; energy cascade: 1) arxiv 2) zenodo slides The baryonic-to-halo mass relation from mass and energy cascade in dark matter flow: 1) arxiv 2) zenodo slides Universal scaling laws and density slope for dark matter haloes: 1) arxiv 2) zenodo slides 3) paper Dark matter halo mass functions and density profiles from mass/energy cascade: 1) arxiv 2) zenodo slides 3) paper Energy cascade for distribution and evolution of supermassive black holes (SMBHs): 2) zenodo slides Condensed slides for all applications "Cascade Theory for Turbulence, Dark Matter, and bulge-SMBH evolution " The two relevant datasets and accompanying presentation can be found at: Dark matter flow dataset Part I: Halo-based statistics from cosmological N-body simulation Dark matter flow dataset Part II: Correlation-based statistics from cosmological N-body simulation. A comparative study of Dark matter flow &amp; hydrodynamic turbulence and its applications The same dataset also available on Github at: Github: dark_matter_flow_dataset and zenodo at: Dark matter flow dataset from cosmological N-body simulation. Cascade and statistical theory developed by these datasets: Inverse mass cascade in dark matter flow and effects on halo mass functions: 1) arxiv 2) zenodo slides Inverse mass cascade and effects on halo deformation, energy, size, and density profiles: 1) arxiv 2) zenodo slides Inverse energy cascade in dark matter flow and effects of halo shape: 1) arxiv 2) zenodo slides The mean flow, velocity dispersion, energy transfer and evolution of dark matter halos: 1) arxiv 2) zenodo slides Two-body collapse model and generalized stable clustering hypothesis for pairwise velocity 1) arxiv 2) zenodo slides Energy, momentum, spin parameter in dark matter flow and integral constants of motion: 1) arxiv 2) zenodo slides Maximum entropy distributions of dark matter in ΛCDM cosmology: 1) arxiv 2) zenodo slides 3) paper Halo mass functions from maximum entropy distributions in dark matter flow: 1) arxiv 2) zenodo slides On the statistical theory of self-gravitating collisionless dark matter flow: 1) arxiv 2) zenodo slides 3) paper High order kinematic and dynamic relations for velocity correlations in dark matter flow: 1) arxiv 2) zenodo slides Evolution of density and velocity distributions and two-thirds law for pairwise velocity: 1) arxiv 2) zenodo slides
description: Conference presentation slides