Zeldovichfaktor

The Zeldovich factor, also known as the Zeldovich approximation, is a concept in cosmology and astrophysics that describes the evolution of density perturbations in the early universe. It is named after the Soviet astrophysicist Yakov Borisovich Zeldovich, who first derived it in 1970. The Zeldovich factor is particularly useful in the study of the formation of large-scale structures, such as galaxies and galaxy clusters, from small initial density fluctuations.

The Zeldovich approximation assumes that the initial density perturbations are small and that the velocity field is irrotational. It provides a simple analytical solution for the evolution of these perturbations, which can be used to understand the growth of structures in the universe. The Zeldovich factor is defined as the ratio of the density perturbation to the mean density of the universe, and it evolves according to a simple power-law relationship.

One of the key features of the Zeldovich approximation is that it predicts the formation of pancake-like structures, which are thin sheets of matter that form as the density perturbations grow. These pancakes are thought to be the precursors to the filaments and nodes that make up the cosmic web, the large-scale structure of the universe.

The Zeldovich approximation has been widely used in numerical simulations of structure formation, and it has been shown to provide a good description of the evolution of density perturbations in the early universe. However, it is important to note that the Zeldovich approximation is a linear theory, and it breaks down in the highly nonlinear regime of structure formation. In this regime, more sophisticated numerical simulations are required to accurately model the evolution of density perturbations.