Nature of dark energy: cosmological constant versus dynamical origin

Determine whether dark energy is a constant vacuum energy (cosmological constant) or a dynamical component that varies in time and/or space.

Background

In discussing assumptions relevant to Conformal Cyclic Cosmology and the broader concordance model, the text highlights the unresolved status of dark energy’s nature. Establishing whether it is strictly a cosmological constant or a dynamical field remains an open observational and theoretical challenge.

References

However, one of the biggest conundrums of science is the question of whether dark energy is actually non-dynamical like the cosmological constant or whether it is perhaps a time (and space) varying quantity. Currently, we do not know the answer to this question.

— Did the Big Bang and cosmic inflation really happen? (A tale of alternative cosmological models)  (2404.18503 - Postolak, 2024) in Conformal Cyclic Cosmology — Problematic assumptions (?) subsection

We do not know whether Euclid, Rubin, and other experiments will support the ``phantom crossing'' results of DESI or will move us back to ΛCDM and CC.

— Quintessential α-attractors, updated  (2608.19781 - Kallosh et al., 20 Aug 2026) in Section 1, Introduction

Future cosmological surveys will provide more stringent tests of these interacting emergent DE scenarios and clarify whether they can play a significant role in the late-time evolution of the Universe.

— Late-Time Emergence of Dark Energy and Its Interaction with Dark Matter  (2609.04990 - Zhang et al., 4 Sep 2026) in Section Summary and Conclusions