# Transients from Initial Conditions Based on Lagrangian Perturbation Theory in $N$-body Simulations III: The Case of GADGET-2 Code

## TL;DR

This paper investigates the impact of third-order Lagrangian perturbation (3LPT) on initial conditions in GADGET-2 cosmological simulations, comparing non-Gaussianity to lower-order methods to improve prediction accuracy.

## Contribution

It introduces the application of 3LPT to GADGET-2 initial conditions and evaluates its effects on matter density field statistics, particularly non-Gaussianity.

## Key findings

- 3LPT affects the statistical properties of initial conditions.
- 2LPT remains valid for certain cosmological predictions.
- Comparison shows differences in non-Gaussianity between perturbation orders.

## Abstract

In modern cosmology, the precision of the theoretical prediction is increasingly required. In cosmological $N$-body simulations, the effect of higher-order Lagrangian perturbation on the initial conditions appears in terms of statistical quantities of matter density field. We have considered the effect of third-order Lagrangian perturbation (3LPT) on the initial conditions, which can be applied to Gadget-2 code. Then, as statistical quantities, non-Gaussianity of matter density field has been compared between cases of different order perturbations for the initial conditions. Then, we demonstrate the validity of the initial conditions with second-order Lagrangian perturbation (2LPT).

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Source: https://tomesphere.com/paper/1901.09210