Apparent versus true value of the cosmological constant

TL;DR

This paper explores how local inhomogeneities in the universe can cause a discrepancy between the apparent and true values of the cosmological constant, emphasizing the importance of considering inhomogeneities in cosmological measurements.

Contribution

It models local inhomogeneities using a { extLambda}LTB solution to differentiate between apparent and true cosmological constant values.

Findings

Local inhomogeneities can significantly affect the apparent value of the cosmological constant.

Modeling with { extLambda}LTB reveals the potential systematic bias in cosmological data interpretation.

Distinguishing between apparent and true values is crucial for accurate cosmological understanding.

Abstract

Supernovae observations strongly support the presence of a cosmological constant, but its value, which we will call apparent, is normally determined assuming that the universe can be accurately described by a homogeneous model. Even in the presence of a cosmological constant we cannot exclude nevertheless the presence of a small local inhomogeneity which could affect the apparent value of the cosmological constant. Neglecting the presence of the inhomogeneity can in fact introduce a systematic misinterpretation of cosmological data, leading to the distinction between an apparent and the true value of the cosmological constant. But is such a difference distinguishable? Recently we set out to model the local inhomogeneity with a {\Lambda}LTB solution and computed the relation between the apparent and the true value of the cosmological constant. In this essay we reproduce the essence of our model with the emphasis on its physical implications.