Energy Conservation, Decoherence Dilution, and the Interpretation of Cosmic End States in Expanding Spacetimes

Description: This theoretical study revisits the interpretation of cosmological end scenarios—such as heat death and asymptotic de Sitter expansion—through the framework of quantum decoherence and energy conservation in expanding spacetimes. Rather than treating late-time cosmology as an absolute termination of physical reality, the paper distinguishes between dynamical cessation and ontological nonexistence. Using explicit calculations of decoherence rates in FLRW backgrounds, we demonstrate that when environmental particle densities dilute as (a(t)^{-3}), the integrated decoherence over infinite future time can remain finite. Under such conditions, quantum superpositions formed beyond a critical cosmological time may never fully decohere. This does not imply recoherence, cyclic cosmology, or violation of thermodynamic irreversibility. Instead, it reflects the asymptotic disappearance of environmental interaction channels that dynamically sustain classical pointer states. The work therefore proposes that late-time cosmic evolution may be more coherently interpreted as a transition from environmentally enforced classicality to a regime of dominant quantum description. The analysis integrates principles from quantum field theory in curved spacetime, decoherence theory, and cosmological expansion dynamics, offering a conceptual clarification of what is meant by a “cosmic end.” 🔹 Keywords: Quantum cosmology; Quantum superposition; Decoherence; Early universe; Late universe; Environmental noise; Quantum–classical transition; Interaction density; Foundations of physics; Conceptual physics