Reheating without an inflaton: metriplectic relaxation of the vacuum structure in the Theory of Structural Articulation (TSA)

We propose a non-inflationary reheating scenario within the Theory of Structural Articulation (TSA), in which the early Universe undergoes a relaxation process governed by metriplectic dynamics rather than by scalar-field–driven inflation. Reheating is described as the dissipation of structural conflict in the vacuum network, leading to an entropy-driven expansion characterized by a universal power-law decay of excess energy, E(t)∼t−1/5E(t) \sim t^{-1/5}E(t)∼t−1/5. This exponent emerges from geometric constraints of the articulation dynamics and does not rely on fine-tuning or slow-roll assumptions. The framework naturally explains several key cosmological features: (i) the absence of a primordial tensor background due to the dissipative nature of the process; (ii) near-Gaussian scalar perturbations as a consequence of entropy maximization; and (iii) a scalar spectral index consistent with observational data at leading order. Unlike inflationary models, the proposed mechanism does not require a fundamental inflaton field or a potential-dominated vacuum state. Instead, cosmological expansion and thermalization arise from structural relaxation of the vacuum itself. The scenario is predictive, falsifiable, and compatible with current observational constraints, providing an alternative pathway for reheating and early-Universe dynamics grounded in non-equilibrium statistical physics and topology.