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.
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 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
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 investigate the process of quantum teleportation in an expanding universe modeled by Friedmann-Robertson-Walker spacetime, focusing on two cosmologically relevant scenarios: a power-law expansion and the de Sitter universe. Adopting a field-theoretical approach, we analyze the quantum correlations between two comoving observers who share an entangled mode of a scalar field. Using the Bogoliubov transformation, we compute the teleportation fidelity and examine its dependence on the expansion rate, initial entanglement, and the mode frequency. Our findings indicate that spacetime curvature and the underlying cosmological background significantly affect the efficiency of quantum teleportation, particularly through mode mixing and vacuum structure. We also compare our results with the flat Minkowski case to highlight the role of cosmic expansion in degrading or preserving quantum information.
This work proposes a theoretical framework in which entropy is treated as a geometric degree of freedom in an extended quantum state space. By introducing a resolution parameter defined as the inverse of von Neumann entropy, an informational metric is constructed on the space of density matrices. Within this framework, a causal structure emerges from a null condition on the metric, defining a light-cone-like boundary for the propagation of quantum correlations. Entanglement propagation is derived and shown to depend on entropy evolution, leading to a dynamical causal structure. In the near-equilibrium limit, the model reproduces a Lieb–Robinson-type bound with finite correlation speed. Connections to holography are established by interpreting entropy as a radial coordinate controlling scale, and an analogue of the Ryu–Takayanagi relation is derived, where entropy corresponds to the length of minimal curves in the informational geometry. Black hole horizons are interpreted as maximal entropy surfaces corresponding to a collapse of distinguishability in quantum state space. The framework suggests that spacetime geometry, causality, and gravitational behavior may emerge from entropy-weighted quantum information structure. This work is an independent theoretical exploration aimed at providing a unified perspective linking quantum information, geometry, and gravity.
Abstract The ontological status of time remains unresolved in fundamental physics. In quantum mechanics, time appears as an external classical parameter, whereas in general relativity it is dynamical and intertwined with spacetime geometry. Canonical approaches to quantum gravity, most notably the Wheeler–DeWitt formulation, eliminate time altogether, leading to the well-known “problem of time.” These tensions motivate frameworks in which time is not fundamental but emergent. In this work, we propose a discrete, update-based framework in which the universe evolves through a sequence of global quantum states indexed by an abstract update parameter rather than by a physical time coordinate. Evolution is formulated as a completely positive, trace-preserving (CPTP) quantum channel acting on the universal density operator, ensuring exact conservation of probability and global quantum information at every update. The framework is deliberately conservative: it preserves the formal structure of quantum mechanics and quantum field theory, enforces vacuum stability, and supports global conservation laws without introducing new dynamical postulates. Within this setting, time emerges relationally at the level of subsystems. As subsystems become increasingly entangled with their environments, entropy gradients arise that define an effective arrow of time, closely aligned with the thermodynamic arrow. The resulting temporal flow is relative, statistical, and observer-dependent, while the global evolution remains information-preserving and, in the closed-system limit, reversible. We explore the implications of this framework for cosmology and black hole physics. The Big Bang is reinterpreted as an initial quantum state rather than a singular beginning of time, avoiding temporal singularities. Black hole evaporation is shown to be compatible with unitary evolution when the full quantum state is considered, naturally reproducing the expected Page curve and resolving the apparent information paradox. Overall, the framework provides a coherent, minimal setting in which time, irreversibility, and cosmological history emerge from quantum correlations rather than from a fundamental temporal background.
This preprint develops a unified coherence-based formulation of physical time grounded in the χ–η–I invariant structure of the Aletheia framework. Across quantum, thermodynamic, gravitational, and cosmological regimes, the paper introduces a scalar coherence potential Ψ constructed from purity, entropy, and structural persistence, and proposes that the physical time increment satisfies the differential law: dt = –κ dΨ In this formulation, time flow is the measurable rate at which coherence is depleted through decoherence, coarse-graining, or environmental coupling. When Ψ is constant—as in globally stationary, Page–Wootters–style quantum states—no internal time elapses. When coherence degrades, time emerges as the bookkeeping of informational loss. The paper demonstrates that this temporal-coupling law naturally reproduces: Thermodynamic time in the macroscopic limit (dt ∝ dS), Quantum decoherence arrows in open-system dynamics, Proper-time–like behavior in weakly decohering or isolated systems, Cosmological time flow via mode decoherence in an expanding FRW universe. Explicit models including qubit dephasing, Lindblad oscillators, and cosmological field modes illustrate how temporal coupling unifies arrows of time across domains traditionally treated with separate frameworks. This formulation provides a coherence-theoretic bridge between general relativity, quantum decoherence, and thermodynamic irreversibility, offering an empirically grounded alternative to conventional parameter-time, thermal time, and entanglement-clock approaches.