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Testing gravity using the environmental dependence of dark matter halos.

Gong-Bo Zhao1, Baojiu Li, Kazuya Koyama

  • 1Institute of Cosmology & Gravitation, University of Portsmouth, United Kingdom.

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Modified gravity theories show environmental differences in dark matter halo masses. This difference, dependent on the environment, can be used to observationally test general relativity (GR).

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Area of Science:

  • Cosmology
  • Astrophysics
  • Theoretical Physics

Background:

  • The accelerated expansion of the Universe is often attributed to dark energy.
  • Alternative theories propose modifications to general relativity (GR) to explain this acceleration.
  • Dark matter halos are fundamental structures in the Universe, and their properties are sensitive to gravity theories.

Purpose of the Study:

  • To investigate the environmental dependence of dark matter halos in modified gravity theories.
  • To determine if observable differences exist between dark matter halo masses predicted by modified gravity and GR.
  • To identify potential observational tests for distinguishing between GR and modified gravity models.

Main Methods:

  • High-resolution N-body simulations were employed.
  • Simulations were conducted within f(R) gravity models incorporating the chameleon mechanism.
  • The lensing and dynamical masses of dark matter halos were compared across different environmental densities.

Main Results:

  • A significant environmental dependence was found in the properties of dark matter halos.
  • The lensing and dynamical masses of halos show a discrepancy that varies with the environment.
  • This environmental effect is predicted by f(R) gravity but not by standard general relativity.

Conclusions:

  • The environmental dependence of dark matter halo properties serves as a potential observational signature for modified gravity.
  • This finding provides a novel method to observationally test and constrain theories that modify general relativity.
  • Distinguishing between GR and f(R) gravity is possible by analyzing halo properties in diverse cosmic environments.