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Topological Saturation of the Page Curve in Geometrically Decoupled Spin Networks

Wenjun Luo

Published Oct 25, 2026• 0 citations
Publisher

Abstract

The core of the black hole information paradox lies in whether Hawking radiation leads to information loss. Based on connectivity engineering, we construct a minimal, gravity-free spin network. By calculating the mutual information and fidelity across different bipartition sizes, we reproduce the complete Page curve. Numerical results show that the peak of mutual information in the geometrically decoupled network (k=3) exhibits a non-trivial scaling behavior with the connectivity k, and reaches saturation at k=3 (with a peak approximately 1.49 times that of the normal network). This not only reveals the reshaping of entanglement capacity by geometric topology but also establishes a topological upper bound for the Page curve peak. Fidelity analysis further reveals that in the late stages of evaporation, the residual subsystem tends towards purification, with the target state fidelity significantly rising to approximately 0.52, which is weakly sensitive to k. This indicates that information is not completely thermalized but exists in a highly compressed global correlation form within the entanglement structure of the black hole residue and external radiation. This model provides a deterministic and strictly reproducible discrete physical benchmark for studying black hole information dynamics.

DOI
10.5281/zenodo.23640624

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The core of the black hole information paradox lies in whether Hawking radiation leads to information loss. Based on connectivity engineering, we construct a minimal, gravity-free spin network. By calculating the mutual information and fidelity across different bipartition sizes, we reproduce the complete Page curve. Numerical results show that the peak of mutual information in the geometrically decoupled network (k=3) exhibits a non-trivial scaling behavior with the connectivity k, and reaches saturation at k=3 (with a peak approximately 1.49 times that of the normal network). This not only reveals the reshaping of entanglement capacity by geometric topology but also establishes a topological upper bound for the Page curve peak. Fidelity analysis further reveals that in the late stages of evaporation, the residual subsystem tends towards purification, with the target state fidelity significantly rising to approximately 0.52, which is weakly sensitive to k. This indicates that information is not completely thermalized but exists in a highly compressed global correlation form within the entanglement structure of the black hole residue and external radiation. This model provides a deterministic and strictly reproducible discrete physical benchmark for studying black hole information dynamics.
The core of the black hole information paradox is whether information falling into the horizon is completely lost during Hawking radiation. Based on connectivity engineering, this paper constructs a one-dimensional spin network with an effective horizon structure. We divide the system into a black hole interior (A) and exterior radiation (B), introducing a cross-horizon tunneling coupling ε. Numerical simulations show that the fidelity of the initial state in region A decays rapidly and plateaus, exhibiting a local information loss illusion; however, the quantum mutual information between regions A and B increases significantly. Furthermore, decoding operations based on the Hayden-Preskill protocol elevate the recovery fidelity to above 0.7 (far exceeding the random baseline), and the maximum entanglement capacity approaches the theoretical maximum 2 ln dim(A). This model requires no gravitational degrees of freedom and relies purely on many-body unitary evolution, providing a minimal deterministic dynamical example for the microscopic implementation of information conservation in Hawking radiation.
The black-hole information paradox is usually formulated as a conflict between two semiclassical statements: Hawking evaporation appears to radiate away mass in a nearly thermal manner, while unitary quantum dynamics forbids the destruction of information. In this paper we construct a macroscopic black-hole surrogate inside the discrete, background-free Quantum Graph Emergent Field Theory (QGEFT) and track both horizon-entanglement proxies and the topological fate of explicitly injected information. Starting from a thermalized Unified Phase 3 universe with N = 1024 sites, we force a localized geometric collapse by driving one node to target degree k = 160, then inject a structured quark-like defect whose internal edges are tracked exactly through 100 subsequent Monte Carlo sweeps. The key observable is a horizon cut-size proxy: the number of edges crossing between the black-hole region and the exterior vacuum, together with a normalized entanglement proxy built from that cut. In the present benchmark the horizon cut-size rises from 1027 to a peak of 1030 edges at sweep 1, while the normalized cut-based entanglement proxy rises from 2.7483 to 2.7563, then trends downward with fluctuations to 2.5941 by sweep 100 as the black-hole core shrinks from degree 161 to 132. At the same time, direct tracking of the infalling quark reveals incomplete local reconstruction: only 25% of the tracked edges appear outside the horizon as distinct edges at any given sampled frame, and the best structural-overlap score reaches only 0.3946. The narrow conclusion supported by the current data is therefore mixed. The black hole exhibits a real topological evaporation channel and a measurable Page-like turnover in the horizon entanglement proxy, but local observables remain Hawking-leaning and do not by themselves recover the full infalling structure. In the QGEFT interpretation, this is evidence for fast scrambling rather than literal information destruction: the information is not recovered as a small intact motif, but is dispersed into the global topological microstate of the graph.
One-shot decoupling is a powerful primitive in quantum information theory and was hypothesized to play a role in the black hole information paradox. We study black hole dynamics modeled by a trilinear Hamiltonian whose semiclassical limit gives rise to Hawking radiation. An explicit numerical calculation of the discretized path integral of the S matrix shows that decoupling is exact in the continuous limit, implying that quantum information is perfectly transferred from the black hole to radiation. A striking consequence of decoupling is the emergence of an output radiation entropy profile that follows Page's prediction. We argue that information transfer and the emergence of Page curves is a robust feature of any multilinear interaction Hamiltonian with a bounded spectrum.
In this work, we give two proposals regarding the status of connectivity of entanglement wedges and the associated saturation of mutual information. The first proposal has been given for the scenario before the Page time depicting the fact that at a particular value of the observer's time tb=tR{t}_{b}={t}_{R}tb​=tR​ (where ${t}_{R}\ensuremath{\ll}\ensuremath{\beta}$), the mutual information $I({R}_{+}:{R}_{\ensuremath{-}})$ vanishes representing the disconnected phase of the radiation entanglement wedge. We argue that this time is the Hartman-Maldacena time at which the fine-grained entropy of radiation goes as $S(R)\ensuremath{\sim}\mathrm{log}(\ensuremath{\beta})$, where $\ensuremath{\beta}$ is the inverse of Hawking temperature of the black hole. On the other hand, the second proposal probes the crucial role played by the mutual information of black hole subsystems in obtaining the correct Page curve of radiation.
The black hole information paradox has been substantially resolved: entropy is preserved in Hawking radiation, as established by the Page curve, replica wormhole calculations, and the island formula. We argue, however, that this resolution addresses only one of two physically distinct properties of quantum information states. The Shannon–Bekenstein framework formalises entropic content S(σ), but lacks representation for a second property: the capacity of a state to causally influence future configurations of external systems. We term this generative capacity G(σ) and establish that it is formally independent of S(σ). The central result is that even in a fully unitary resolution, I(ρ_rad, ρ_E) ≤ C·S_BH·2^{−S_BH/2} → 0 after the scrambling time for any system E in prior causal contact with an infalling state, while S(ρ_rad) follows the Page curve. A unitary resolution restores entropy; it does not restore causal influence capacity. We demonstrate this in the JT gravity + bath model via the decoupling theorem. Eight technical contributions support this framework: formal proof of S–G independence via the Rindler family; proof that the Bell state saturates the supremum in G(σ,d) via the entanglement-assisted channel capacity theorem; three explicit benchmark calculations; covariant reformulation of G bounded above by an area law; distinction of the causal residue from BMS soft hair charges; and time-dependent causal sterilization at rate κ = 2πT_H = λ_L, saturating the Maldacena–Shenker–Stanford bound on quantum chaos [35]. Theorem C.2 establishes that classical correlations survive the Rindler horizon completely while quantum entanglement is destroyed — the horizon acts as a quantum-classical separator. The framework introduces the causal quality index κ ∈ [1,2] as a potentially observable signature distinguishing accretion histories with identical mass, charge, and angular momentum.
The complete evaporation of black holes, as a natural endpoint of Hawking radiation, gives rise to the black hole information paradox, which fundamentally challenges the principles of unitarity and information conservation in quantum mechanics. Although the AdS/CFT correspondence indicates that information is preserved during black hole evaporation, the precise mechanism by which it is recovered from the Hawking radiation remains an open question. To explore a potential resolution, we investigate information transfer in a spin-chain model featuring an effective horizon realized via position-dependent couplings within an XY spin chain. We derive and demonstrate Page curve-like behavior, and analyze the transmission of quantum resources, such as entanglement and coherence, across the effective horizon. Our results show that quantum resources initially localized within an interior subsystem can be transferred to the exterior via particle radiation through the horizon. This study provides a novel perspective from quantum simulation on how information may escape from black holes, thereby contributing to the further understanding of the black hole information paradox.