Contemporary Philosophical Perspectives on the Cosmological Constant

TL;DR

This paper critically examines the philosophical assumptions underlying the use of the cosmological constant in modern cosmology, highlighting distinctions, methodological issues, and the role of principles like the anthropic principle.

Contribution

It offers a systematic assessment of philosophical assumptions in precision cosmology, especially regarding dark energy and the cosmological constant, clarifying their conceptual and methodological implications.

Findings

Distinguishes between different explanations for accelerated expansion

Highlights the role of background assumptions and principles in cosmological tests

Argues that some principles are necessary but unprovable, others unjustified

Abstract

The (re)introduction of $\Lambda$ into cosmology has spurred debates that touch on central questions in philosophy of science, as well as the foundations of general relativity and particle physics. We provide a systematic assessment of the often implicit philosophical assumptions guiding the methodology of precision cosmology in relation to dark energy. We start by briefly introducing a recent account of scientific progress in terms of risky and constrained lines of inquiry. This allows us to contrast aspects of $\Lambda$ that make it relevantly different from other theoretical entities in science, such as its remoteness from direct observation or manipulability. We lay out a classification for possible ways to explain apparent accelerated expansion but conclude that these conceptually clear distinctions may blur heavily in practice. Finally, we consider the important role played in cosmology by critical tests of background assumptions, approximation techniques, and core principles, arguing that the weak anthropic principle fits into this category. We argue that some core typicality assumptions -- like the Copernican principle and the cosmological principle -- are necessary though not provable, while others -- like the strong anthropic principle and appeals to naturalness or probability in the multiverse -- are not similarly justifiable.