Origin of dark energy

Ascertain the physical mechanism driving the observed accelerated expansion of the universe, including determining whether it is due to a cosmological constant or alternative dynamical phenomena, consistent with cosmological observations and theoretical constraints.

Background

Observations of type Ia supernovae and other cosmological probes indicate an accelerating universe that current models struggle to explain without introducing dark energy, often modelled via a cosmological constant.

The author identifies dark energy as one of the two major open observational problems; whether and how it should inform quantum gravity research remains debated, but resolving it is central to a complete cosmological theory.

References

Nevertheless, there are some open problems related to observations. The two biggest ones are the problems of dark matter and dark energy.

— Why Do We Want a Theory of Quantum Gravity?  (2505.04858 - Crowther, 7 May 2025) in Section 1.3 (Empirical constraints), Empirical results not explained by current theories

The physical origin of cosmic acceleration therefore remains an open question and motivates the study of gravitational theories beyond GR.

— Testing $f(Q)$ Gravity with DESI DR2 and Strong-Lensing Time Delays  (2608.24676 - Kumar et al., 25 Aug 2026) in Section 1, Introduction

However, it remains unclear whether cosmic acceleration is driven by a new energy component, commonly referred to as dark energy, or reflects departures from the standard description of gravity on cosmological scales.

— 3.5-meter Segmented-Mirror Robotic Space Telescope Mission White Paper I. Overall Architecture and Scientific Mission  (2609.02571 - Kang et al., 2 Sep 2026) in Chapter 4, Chapter 4, Scientific Objectives, Section Cosmology, subsection Cosmic Acceleration, Dark Energy, and Dark Matter