The "Inside of the Universe" in the Light Universe Theory -- Model Simplification and the Possibility of Considering an Outside --

This paper examines the relationship between simplified cosmological models and the universe itself. It distinguishes between what a model does not consider and what does not exist in reality, focusing particularly on the possibility of considering an “outside of the universe.” The paper does not claim that such an outside exists. Instead, it asks whether excluding the possibility at the modeling stage may also prevent alternative theories that require an outside from being considered.