This article derives the entropy associated with the large-scale structure of the Universe in the linear regime, where the Universe can be described by a perturbed Friedmann-Lema\^{\i}tre spacetime. In particular, it compares two different definitions proposed in the literature for the entropy using a spatial averaging prescription. For one definition, the entropy of the large-scale structure and for a given comoving volume always grows with time, both for a CDM and a ΛCDM model. In particular, while it diverges for a CDM model, it saturates to a constant value in the presence of a cosmological constant. The use of a light-cone averaging prescription in the context of the evaluation of the entropy is also discussed.

## Address

Département de Physique Théorique

Université de Genève

24, quai Ernest Ansermet

1211 Genève 4

Switzerland

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