English

Universal spectrum and scaling laws for halo mass function, structure, and dark matter mass constraints

Cosmology and Nongalactic Astrophysics 2025-12-02 v4 Astrophysics of Galaxies Fluid Dynamics

Abstract

Between the linear and nonlinear regimes, we identify a universal transition range centered on a characteristic halo mass mhtm_h^*\propto t, within which gravitational dynamics self-organize the matter field toward an effective spectral index n=-1. In a bottom-up hierarchy, early collapse of low-mass halos preserves imprints of the primordial spectrum, whereas prolonged assembly of halos near mhm_h^* erases that memory and establishes universality. We formulate a scale-to-scale cascade, the redistribution of mass and energy across scales, that yields universal scaling laws for the halo mass function and internal structure. Globally, the cascade drives a random walk of halos with mass-dependent waiting time τgmhλ\tau_g\propto m_h^{-\lambda}; A Fokker-Planck equation gives mass function fMmhλf_M\propto m_h^{-\lambda} and λ=2/3\lambda=2/3 for the gravity-dominant transition range. Locally, a radially directed cascade governs particle migration with waiting time τgrrγ\tau_{gr}\propto r^{-\gamma}, yielding density ρrr2γ\rho_r\propto r^{-2\gamma} and γ=2/3\gamma=2/3 on scales near mhm_h^*. The cascade drives the system toward a statistically steady state that continuously releases energy and maximizes entropy, characterized by scale-independent rates, preventing mass or energy buildup at intermediate scales. Scale-dependent dominance of the primordial spectrum versus gravity implies two effective exponents, producing double-λ\lambda mass functions and double-γ\gamma density in excellent agreement with simulations. Using Illustris and Virgo, we measure an inverse kinetic-energy cascade from small to large scales at εu107\varepsilon_u \approx -10^{-7}m2^2/s3^3, a direct potential-energy cascade of 1.4εu-1.4\varepsilon_u, and a net dissipation of -0.4εu\varepsilon_u via halo mergers and particle migration. The dependence of waiting time and step length on the particle mass suggests new constraints near 101210^{12}GeV.

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Cite

@article{arxiv.2109.09985,
  title  = {Universal spectrum and scaling laws for halo mass function, structure, and dark matter mass constraints},
  author = {Zhijie Xu},
  journal= {arXiv preprint arXiv:2109.09985},
  year   = {2025}
}

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