This work presents a phenomenological cosmological framework in which the large-scale evolution of the universe is described as a continuous phase-transition process governed by a relaxation-time order parameter τ. The parameter τ interpolates between non-localized, radiation-like energy states and fully crystallized mass configurations, providing a unified description of the radiation-to-matter transition without introducing new dynamical degrees of freedom. Building upon an earlier three-phase formulation, this version introduces a four-phase physical interpretation—plasma, gas, liquid, and solid phases of light—while preserving the original mathematical structure. In this interpretation, dark energy, dark matter, the present cosmological phase, and black holes are understood as different phase manifestations of the same underlying energy medium, rather than distinct fundamental entities. The framework explicitly enforces local energy conservation through interaction terms linking radiation and matter components and remains consistent with standard cosmological observations, including the cosmic microwave background, large-scale structure, and local precision tests of the speed of light. A key distinguishing feature of the model is a falsifiable observational prediction: a non-monotonic feature (knee or peak) in the stochastic gravitational wave background generated by anisotropic stress at phase-transition boundaries during the formation of the liquid phase. This signature is potentially detectable by future space-based gravitational wave observatories. This Zenodo record serves as a DOI-registered preprint establishing priority for the proposed phase-transition cosmology and its four-phase reinterpretation.Note on Version 2.1: This version consolidates the formal mathematical dynamics of the tau-field with the comprehensive four-phase physical interpretation.
Kazuyuki Kondo (Thu,) studied this question.