We propose that environment-induced decoherence during cosmic expansion was selective rather than uniform. Applying Zurek's einselection framework to cosmology, we argue that expansion-compatible quantum states (pointer states) survived to become classical matter and structure, while expansion-incompatible states (non-pointer states) rapidly diluted into background entropy. Using quantum field theory in FLRW spacetime, we derive the selectivity parameter β ≈ 2-5 and Gaussian horizon-compatibility function f(x_k) = exp[-(ln x_k)²/(2σ²)] from first principles via pointer state condition (minimization of interaction Hamiltonian) combined with adiabaticity analysis in expanding spacetime. The horizon scale x_k = k/(aH) = 1 emerges naturally from variational principle, not as an assumption. Numerical integration yields survival fraction f_survival ≈ 20-50%, explaining why this fraction of primordial quantum states persists as classical degrees of freedom. The framework contains no free parameters beyond standard FLRW cosmology. Predictions: (1) decoherence timescale τ_d ≈ β × τ_H (fundamentally derived); (2) scale-dependent modifications to matter power spectrum P(k) ∝ f(k/aH); (3) observable signatures in CMB power spectrum anomalies and large-scale structure formation patterns testable by Planck, Euclid, and DESI within 5-10 years.
We propose that environment-induced decoherence during cosmic expansion was selective rather than uniform. Applying Zurek's einselection framework to cosmology, we argue that expansion-compatible quantum states (pointer states) survived to become classical matter and structure, while expansion-incompatible states (non-pointer states) rapidly diluted into background entropy. Using quantum field theory in FLRW spacetime, we derive the selectivity parameter β ≈ 2-5 and Gaussian horizon-compatibility function f(x_k) = exp[-(ln x_k)²/(2σ²)] from first principles via pointer state condition (minimization of interaction Hamiltonian) combined with adiabaticity analysis in expanding spacetime. The horizon scale x_k = k/(aH) = 1 emerges naturally from variational principle, not as an assumption. Numerical integration yields survival fraction f_survival ≈ 20-50%, explaining why this fraction of primordial quantum states persists as classical degrees of freedom. The framework contains no free parameters beyond standard FLRW cosmology. Predictions: (1) decoherence timescale τ_d ≈ β × τ_H (fundamentally derived); (2) scale-dependent modifications to matter power spectrum P(k) ∝ f(k/aH); (3) observable signatures in CMB power spectrum anomalies and large-scale structure formation patterns testable by Planck, Euclid, and DESI within 5-10 years.
This paper presents my finding that quantum decoherence during the universe's expansion selected certain states over others. I apply Zurek's well-known einselection concept to cosmology and show that modes near the horizon scale survived, while others decohered into entropy. The main result is that 20-50% of primordial quantum states persisted as classical matter. I derive this from the interaction Hamiltonian without any free parameters. The prediction is testable by Euclid and Planck data within 10 years.
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
The accelerating expansion of the universe, described by the Friedmann–Lemaˆıtre–Robertson– Walker (FLRW) metric, establishes a cosmological event horizon beyond which emitted pho-tons recede at effective velocities exceeding the speed of light (c). While general relativity treats this phenomenon as a geometric boundary resulting in causal disconnection, quantuminformation theory requires an account of the physical fate of quantum information crossing this horizon. In this paper, we propose a theoretical framework wherein cosmic metric ex-pansion acts as a Natural Quantum Eraser. We model the recession of quantum states across the cosmological horizon as a continuous, universe-scale decoherence channel that ir-reversibly erases path information (which-way information) for observers within the local causal patch. By synthesizing the FLRW spacetime metric with the Von Neumann entropy formulation and decoherence theory, we demonstrate that cosmic expansion enforces local-ized wave-function collapse without violating the No-Cloning Theorem or unitary quantum evolution. Furthermore, we show that the information ”erased” by the expanding horizondirectly contributes to the local thermodynamic entropy of the observable universe, offeringa novel quantum-informational foundation for the thermodynamic arrow of time.
Description : This work introduces a novel, model-independent diagnostic framework for quantifying quantum decoherence in primordial inflationary perturbations. The study addresses the fundamental problem of the quantum-to-classical transition in cosmology by defining a normalized persistence functional that captures the suppression of quantum coherence over time. Within an open quantum system approach, each perturbation mode is treated as an effective quantum degree of freedom interacting with an environment, leading to Gaussian suppression of off-diagonal density matrix elements. The proposed functional provides a direct and scalable measure of decoherence efficiency without relying on detailed microscopic modeling. A key feature of the framework is the introduction of a residual coherence parameter, which accounts for possible late-time deviations from complete classicalization. The work further establishes a monotonicity property for the decoherence functional and connects the persistence measure to entropy growth, offering an information-theoretic interpretation of the decoherence process. Importantly, the framework suggests a phenomenological link between residual coherence and observable non-Gaussianity in the cosmic microwave background, opening a pathway for potential observational constraints. The proposed diagnostic functional is broadly applicable across inflationary models and provides a unified tool for comparing decoherence efficiency under different environmental interactions. This work lays the foundation for future studies on quantum signatures in cosmological observables and the persistence of quantum features in the early universe. Keywords : Quantum Decoherence Inflationary Cosmology Primordial Perturbations Open Quantum Systems Quantum-to-Classical Transition Non-Gaussianity Cosmological Perturbation Theory Density Matrix Quantum Cosmology Early Universe Physics Decoherence Functional Entropy and Information Theory
AbstractTime-symmetric and top-down approaches to quantum cosmology—most notably Aharonov’sTwo-State Vector Formalism (TSVF), Wheeler’s Participatory Anthropic Principle, andHawking-Hertog top-down cosmology—address the quantum measurement problem and cosmological fine-tuning by positing a post-selected final boundary state ⟨Φfinal| that constrainsthe early universe’s path integral. However, these frameworks face a persistent foundationalobjection: what selects the final boundary state itself? Postulating a hard-coded final microstate or an explicit teleological rule (such as “maximal integrated complexity”) merelytransfers the fine-tuning problem from the initial boundary (t = 0) to the asymptotic future (t → ∞). In this paper, we propose a non-teleological mechanism in which a uniquefinal boundary condition is dynamically bootstrapped into existence through TemporalQuantum Darwinism. Extending Zurek’s framework of Environment-Induced Superselection (einselection) and pointer-state proliferation to a bidirectional cosmic cavity, wemodel the initial and final boundaries not as externally imposed axioms, but as coupledmirrors in a time-symmetric resonant loop governed by a recursive fixed-point operator⟨Φ∗| = S[⟨Φ∗|]. We demonstrate that candidate cosmic histories dominated by intraenvironment thermal scrambling (Page-curve dynamics) fail to preserve orthogonal pointerrecords at the asymptotic horizon; consequently, their forward and backward propagatorsaccumulate random relative phases and destructively cancel out of the global WheelerDeWitt state (⟨Φscrambled|Ψ⟩ → 0). Conversely, histories whose fundamental constants support non-interacting “star-topology” broadcast channels (e.g., free-streaming photons andgravitons scattering off stable macroscopic structures) achieve massive pointer redundancy(Rδ ≫1). Because pointer states commute with the system-environment interaction Hamiltonian ([ ˆHint, ˆ Πk] = 0), they reflect coherently across the temporal cavity, amplifying viaspectral power iteration into a single, mode-locked 4D fixed-point eigenstate. This synthesis resolves the quantum measurement problem—accounting for the preferred pointerbasis, single-outcome realization without non-unitary collapse or Everettian branching, andthe Born rule—while demonstrating that complexity and observer-participancy emerge asstructural necessities for a quantum timeline to avoid destructive self-cancellation.
In this thesis, we study the decoherence of cosmological scalar perturbations during inflation. We first discuss the FRW model and cosmic inflation. Inflation is a period of accelerated expansion in the early universe, in typical models caused by a scalar field called inflaton. We review cosmological perturbation theory, where perturbations of the inflaton field and scalar degrees of freedom of the metric tensor are combined into the gauge-invariant Sasaki-Mukhanov variable. We quantize this variable using canonical quantization. Then, we discuss how interactions between the perturbations and their environment can lead to decoherence. In decoherence, the reduced density operator of the perturbations becomes diagonal with respect to a particular pointer basis. We argue that the pointer basis for the cosmological scalar perturbations consists of approximate eigenstates of the field value operator. Finally, we discuss how decoherence can help understand the transition from quantum theory to classical perturbation theory, and justify the standard treatment of perturbations and their initial conditions in cosmology. We conclude that since decoherence should not spoil the observationally successful predictions of this standard treatment, it is unlikely that the actual amount of decoherence could be observed in, say, the CMB radiation.