Cosmic Thermal History and Detailed Cosmic Composition

Characterize the complete thermal history of the universe up to the present epoch and determine the detailed composition of the universe’s matter and energy contents within a consistent cosmological framework.

Background

Despite the maturity of the standard cosmological model, the paper emphasizes that key global properties remain incompletely known, including the universe’s full thermal evolution and its detailed composition at large scales.

A comprehensive account would sharpen constraints on dark matter and dark energy, refine early‑ and late‑time cosmology, and integrate multimessenger observations with particle‑physics inputs.

References

There is much that we do not know, including the complete thermal history (to now) of the universe and the detailed composition of the universe at large.

— Perspectives and Questions: Toward an Expansive Agenda for Particle Physics  (2510.06348 - Quigg, 7 Oct 2025) in Section 9, The Cosmic Connection

While these degeneracies could be broken using informative priors on the thermal history of the IGM, it will be up to future work to carefully consider whether such priors are indeed independent.

— Lyman-$α$ forest 1D flux power spectrum constraints on QSO-assisted reionization models  (2609.16992 - Iršič et al., 15 Sep 2026) in Discussion and Conclusions, Section 5

A corresponding production history has not been constructed for our spectra.

— Neutralino Dark Matter in SU(5) after H.E.S.S. and Direct-Detection Searches  (2609.19675 - Ajaib et al., 17 Sep 2026) in Section 3.2, “Full-density assumption and elastic scattering”

The abundances of $N_Sc$, the light states from $N_Dc$, and the flavon phase must therefore be determined for a specified thermal history. If they contribute appreciably to the radiation density, the cosmological mass limits must be reassessed with these contributions included. This thermal analysis is left for future work.

— Non-Invertible Froggatt-Nielsen Symmetry  (2610.21688 - Otsuka et al., 15 Oct 2026) in Section 6.3, subsection “Phenomenological consequences”