### Abstract

We present a numerical study of the cosmic density versus velocity divergence relation (DVDR) in the mildly non-linear regime. We approximate the dark matter as a non-relativistic pressureless fluid, and solve its equations of motion on a grid fixed in comoving coordinates. Unlike N-body schemes, this method yields directly the volume-averaged velocity field. The results of our simulations are compared with the predictions of the third-order perturbation theory (3PT) for the DVDR. We investigate both the mean "forward" relation (density in terms of velocity divergence) and the mean 'inverse' relation (velocity divergence in terms of density), with emphasis on the latter. On scales larger than about 20 Mpc, our code recovers the predictions of the 3PT remarkably well and significantly better than in recent N-body simulations. On scales of a few Mpc, the DVDR predicted by 3PT differs slightly from the simulated one. In particular, approximating the inverse DVDR by a third-order polynomial turns out to give a poor fit. We propose a simple analytical description of the inverse relation, which works well for mildly non-linear scales.

Original language | English (US) |
---|---|

Pages (from-to) | 464-472 |

Number of pages | 9 |

Journal | Monthly Notices of the Royal Astronomical Society |

Volume | 316 |

Issue number | 3 |

State | Published - Aug 11 2000 |

Externally published | Yes |

### Fingerprint

### Keywords

- Cosmology: theory
- Dark matter
- Large-scale structure of Universe
- Methods: numerical

### ASJC Scopus subject areas

- Space and Planetary Science

### Cite this

*Monthly Notices of the Royal Astronomical Society*,

*316*(3), 464-472.

**Reconstructing cosmic peculiar velocities from the mildly non-linear density field.** / Kudlicki, Andrzej; Chodorowski, Michał; Plewa, Tomasz; Rózyczka, Michał.

Research output: Contribution to journal › Article

*Monthly Notices of the Royal Astronomical Society*, vol. 316, no. 3, pp. 464-472.

}

TY - JOUR

T1 - Reconstructing cosmic peculiar velocities from the mildly non-linear density field

AU - Kudlicki, Andrzej

AU - Chodorowski, Michał

AU - Plewa, Tomasz

AU - Rózyczka, Michał

PY - 2000/8/11

Y1 - 2000/8/11

N2 - We present a numerical study of the cosmic density versus velocity divergence relation (DVDR) in the mildly non-linear regime. We approximate the dark matter as a non-relativistic pressureless fluid, and solve its equations of motion on a grid fixed in comoving coordinates. Unlike N-body schemes, this method yields directly the volume-averaged velocity field. The results of our simulations are compared with the predictions of the third-order perturbation theory (3PT) for the DVDR. We investigate both the mean "forward" relation (density in terms of velocity divergence) and the mean 'inverse' relation (velocity divergence in terms of density), with emphasis on the latter. On scales larger than about 20 Mpc, our code recovers the predictions of the 3PT remarkably well and significantly better than in recent N-body simulations. On scales of a few Mpc, the DVDR predicted by 3PT differs slightly from the simulated one. In particular, approximating the inverse DVDR by a third-order polynomial turns out to give a poor fit. We propose a simple analytical description of the inverse relation, which works well for mildly non-linear scales.

AB - We present a numerical study of the cosmic density versus velocity divergence relation (DVDR) in the mildly non-linear regime. We approximate the dark matter as a non-relativistic pressureless fluid, and solve its equations of motion on a grid fixed in comoving coordinates. Unlike N-body schemes, this method yields directly the volume-averaged velocity field. The results of our simulations are compared with the predictions of the third-order perturbation theory (3PT) for the DVDR. We investigate both the mean "forward" relation (density in terms of velocity divergence) and the mean 'inverse' relation (velocity divergence in terms of density), with emphasis on the latter. On scales larger than about 20 Mpc, our code recovers the predictions of the 3PT remarkably well and significantly better than in recent N-body simulations. On scales of a few Mpc, the DVDR predicted by 3PT differs slightly from the simulated one. In particular, approximating the inverse DVDR by a third-order polynomial turns out to give a poor fit. We propose a simple analytical description of the inverse relation, which works well for mildly non-linear scales.

KW - Cosmology: theory

KW - Dark matter

KW - Large-scale structure of Universe

KW - Methods: numerical

UR - http://www.scopus.com/inward/record.url?scp=0001656878&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0001656878&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0001656878

VL - 316

SP - 464

EP - 472

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 3

ER -