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Dark Matter-Dark Energy Interaction and the Shape of Cosmic Voids

Zeinab Rezaei

TL;DR

This paper addresses how non-gravitational DM-DE interaction affects cosmic void shapes. It uses a data-constrained dynamical dark energy model with a coupling parameter $\eta$ and a transfer rate $Q = \dfrac{d\rho^{\rm int}}{dt} = \eta H \rho_{\rm DM}$ to compute the linear growth factor $D(z)$ and the void ellipticity distribution $p(\varepsilon; z)$ via the tidal-shear formalism. The main result is that DM-DE coupling increases the mean $\langle\varepsilon\rangle$ and maximum $\varepsilon_{\max}$ ellipticity, shifting $p(\varepsilon; z)$ toward higher values, with stronger effects at lower redshift and smaller Lagrangian void scales $R_L$. These findings suggest void-shape statistics as a complementary observational probe of dark sector interactions beyond primary CMB and galaxy clustering analyses.

Abstract

Interaction between dark matter and dark energy as one of not completely solved problems in cosmology has been studied extensively. This interaction affects the cosmic structures. In this regard, the shape of cosmic voids can be influenced by the dark matter and dark energy interaction. Here, employing the dynamical dark energy model constrained by the observational data, we study the effects of this interaction on the ellipticity of cosmic voids. To this aim, we apply the linear growth of density perturbation in the presence of interaction. The probability density distribution for the ellipticity of cosmic voids has been investigated. The results confirm that the ellipticity of cosmic voids increases when the dark matter and dark energy interaction is considered.

Dark Matter-Dark Energy Interaction and the Shape of Cosmic Voids

TL;DR

This paper addresses how non-gravitational DM-DE interaction affects cosmic void shapes. It uses a data-constrained dynamical dark energy model with a coupling parameter and a transfer rate to compute the linear growth factor and the void ellipticity distribution via the tidal-shear formalism. The main result is that DM-DE coupling increases the mean and maximum ellipticity, shifting toward higher values, with stronger effects at lower redshift and smaller Lagrangian void scales . These findings suggest void-shape statistics as a complementary observational probe of dark sector interactions beyond primary CMB and galaxy clustering analyses.

Abstract

Interaction between dark matter and dark energy as one of not completely solved problems in cosmology has been studied extensively. This interaction affects the cosmic structures. In this regard, the shape of cosmic voids can be influenced by the dark matter and dark energy interaction. Here, employing the dynamical dark energy model constrained by the observational data, we study the effects of this interaction on the ellipticity of cosmic voids. To this aim, we apply the linear growth of density perturbation in the presence of interaction. The probability density distribution for the ellipticity of cosmic voids has been investigated. The results confirm that the ellipticity of cosmic voids increases when the dark matter and dark energy interaction is considered.

Paper Structure

This paper contains 9 sections, 16 equations, 4 figures.

Table of Contents

  1. Introduction
  2. Cosmological model with dynamical interacting dark energy
  3. Interacting dark sectors
  4. Linear growth of density perturbation
  5. Probability density distribution for the ellipticity of cosmic voids
  6. RESULTS
  7. Mean ellipticity and maximum ellipticity of cosmic voids: Redshift dependency
  8. Mean ellipticity and maximum ellipticity of cosmic voids: Scale dependency
  9. Summary and Conclusions

Figures (4)

  • Figure 21: Linear growth factor, $D$, versus the redshift, $z$, in noninteracting and interacting models.
  • Figure 32: Probability density distribution, $P(\varepsilon)$, in noninteracting and interacting models. The values of the redshift and void scale have been considered as $z=1.0$ and $R_{\rm L}=4 h^{-1}{\rm Mpc}$.
  • Figure 43: Left: mean ellipticity, $<\varepsilon>$, and Right: maximum ellipticity, $\varepsilon_{\rm max}$, of cosmic voids in noninteracting and interacting models versus the redshift, $z$. The value of the void scale has been considered as $R_{\rm L}=4 h^{-1}{\rm Mpc}$.
  • Figure 44: Left: mean ellipticity, $<\varepsilon>$, and Right: maximum ellipticity, $\varepsilon_{\rm max}$, of cosmic voids in noninteracting and interacting models versus the void scale, $R_{\rm L}$. The value of the redshift has been considered as $z=1.0$.