# Pseudo-Evolution of Galaxies in LCDM Cosmology

## TL;DR

This paper investigates how mixing different cosmological models affects perceived galaxy size evolution, revealing that model assumptions can cause significant apparent size changes that mimic actual evolution.

## Contribution

It demonstrates that unintentional mixing of cosmological models can produce spurious galaxy size evolution signals, highlighting the importance of consistent cosmological assumptions in galaxy studies.

## Key findings

- Interpreting galaxy sizes with different cosmologies causes apparent size changes.
- Spurious size evolution factors range from 1.1 to 23.8 depending on models.
- Proper sizes derived from different models are minimally different.

## Abstract

Our knowledge about galaxy evolution comes from transforming observed galaxy properties at different redshifts to co-moving physical scales. This transformation depends on using a cosmological model. Here the effects of unintentional mixing of two different cosmological models on the size evolution of galaxies is studied. As a gedanken experiment, a galaxy of fixed proper size and luminosity is moved across different redshifts. The apparent size of this galaxy is then interpreted with a cosmological model presumed by the observer, which is different compared to the cosmology exhibited by the Universe. In such a case, a spurious size evolution of the galaxy is observed. A galaxy behaving according to the R_h=ct and Neumann's cosmology, when interpreted with the LCDM cosmological model, shows an increase in size by a factor of 1.1 and 1.3 from z=7.5 to z approx. 0, respectively. The apparent size of a galaxy in a static Euclidean cosmology, when interpreted in the LCDM model, shows a factor of 23.8 increase in size between z=7.5 to z approx. 0. This is in close agreement with the observational data with a size increase of a factor of 6.8 between z=3.2 to z approx. 0. Furthermore, using the apparent size data, it is shown that the difference between the derived proper sizes in R_h=ct, Neumann's and LCDM cosmological models are minimal.