Embedded-Observer No-Go TheoremAny closed unitary quantum system — from many-body lattice models to quantum-gravity programs that posit a strictly unitary wavefunction of the universe(causal sets, LQG, CDT, string theory, Everettian decoherence) - contains embedded observers who cannot, in principle, fully self-describe the global stateor evolve autonomously and unitarily once a generic, non-fine-tuned interaction with the rest of the system has occurred even a single time. The result is locality-independent: the proof rests only on closure, the observer's embeddedness, and the genericity of the coupling. "Collapse" and apparent irreversibility cease to be separate postulates - they are a provable consequence of embeddedness itself. The theorem additionally establishes a causal boundary -an exact light cone for discrete quantum circuits, an approximate one (with an exponentially small tail) for general local Hamiltonian systems -together with an operational tool for quantifying the two distinct kinds of limitationon an observer's knowledge: stock (entropy) and flow (channel unitarity).Computational Appendix — The Embedded-Observer No-Go Theorem: https://github.com/SergejMaterov/Embedded_Observer_NoGo
Embedded-Observer No-Go TheoremAny closed unitary quantum system — from many-body lattice models to quantum-gravity programs that posit a strictly unitary wavefunction of the universe(causal sets, LQG, CDT, string theory, Everettian decoherence) - contains embedded observers who cannot, in principle, fully self-describe the global stateor evolve autonomously and unitarily once a generic, non-fine-tuned interaction with the rest of the system has occurred even a single time. The result is locality-independent: the proof rests only on closure, the observer's embeddedness, and the genericity of the coupling. "Collapse" and apparent irreversibility cease to be separate postulates - they are a provable consequence of embeddedness itself. The theorem additionally establishes a causal boundary -an exact light cone for discrete quantum circuits, an approximate one (with an exponentially small tail) for general local Hamiltonian systems -together with an operational tool for quantifying the two distinct kinds of limitationon an observer's knowledge: stock (entropy) and flow (channel unitarity).Computational Appendix — The Embedded-Observer No-Go Theorem: https://github.com/SergejMaterov/Embedded_Observer_NoGo
The Generalized No-Chaos TheoremBounded Complexity Growth at Any Fixed Coarse-GrainingWithin the Quantum Gravity Consistency Framework (QGCF) - any finite-dimensional, closed, unitarily evolving system satisfying (QGCF1)-(QGCF4) - three logically distinct results are established. First, ontic chaos is impossible in three senses: spectral quasiperiodicity, Poincaré recurrence, and exact vanishing of the asymptotic quantum Lyapunov exponent λL (§5). Second, dynamical (Lyapunov/0-1-test) chaos at any FIXED coarse-graining scale ℓ is also impossible, unconditionally - a direct corollary of the same almost-periodicity that gives λL=0 (§7); the one established quantum-chaos diagnostic that survives this obstruction is level (spectral) statistics, checked preliminarily against a non-integrable/integrable benchmark pair (§7.3). Third, and logically independent of the first two: no observer realized as a proper subsystem can simultaneously reconstruct the complete global state from its own accessible data and evolve under an autonomous unitary law, once genuinely (entangling-ly) coupled to the rest of the system (§8) - a consequence of purification non-uniqueness (Hughston-Jozsa-Wootters) and the non-unitary character of open marginal dynamics, requiring no assumption beyond a generic (non-fine-tuned) boundary coupling. The two failures named in that theorem arise from the same physical mechanism - entanglement across the observer's own boundary - but are shown not to be strictly the same fact, only generically co-occurring. Thermalization of coarse blocks (Calabrese-Cardy growth to a Page-value plateau) is real, established physics, distinct from all of the above, and is presented (§9) together with the timescale τ*(ℓ) it requires, and its role as the only available justification for treating the system's effective Hamiltonian Ĥeff as possessing a meaningful temperature Tc, given that the axioms admit no literal external bath. A note on generality. QGCF does not require a literal discrete graph. (QGCF3) is stated as a disjunction: a discrete, graph-based realization (QGCF3a), giving the sharper results of §8.2 and §8.6.2 exactly; or a continuum realization with only a locality/metric structure (QGCF3b), giving the standard, approximately-causal Lieb-Robinson bound instead. Everything else in this document §5-§7, §8.3-§8.6.1, §9 - depends only on finite-dimensionality and unitarity (QGCF1-QGCF2), or on (QGCF4)'s boundedness/genericity, and holds identically under either branch of (QGCF3).
The Generalized No-Chaos TheoremBounded Complexity Growth at Any Fixed Coarse-GrainingWithin the Quantum Gravity Consistency Framework (QGCF) - any finite-dimensional, closed, unitarily evolving system satisfying (QGCF1)-(QGCF4) - three logically distinct results are established. First, ontic chaos is impossible in three senses: spectral quasiperiodicity, Poincaré recurrence, and exact vanishing of the asymptotic quantum Lyapunov exponent λL (§5). Second, dynamical (Lyapunov/0-1-test) chaos at any FIXED coarse-graining scale ℓ is also impossible, unconditionally - a direct corollary of the same almost-periodicity that gives λL=0 (§7); the one established quantum-chaos diagnostic that survives this obstruction is level (spectral) statistics, checked preliminarily against a non-integrable/integrable benchmark pair (§7.3). Third, and logically independent of the first two: no observer realized as a proper subsystem can simultaneously reconstruct the complete global state from its own accessible data and evolve under an autonomous unitary law, once genuinely (entangling-ly) coupled to the rest of the system (§8) - a consequence of purification non-uniqueness (Hughston-Jozsa-Wootters) and the non-unitary character of open marginal dynamics, requiring no assumption beyond a generic (non-fine-tuned) boundary coupling. The two failures named in that theorem arise from the same physical mechanism - entanglement across the observer's own boundary - but are shown not to be strictly the same fact, only generically co-occurring. Thermalization of coarse blocks (Calabrese-Cardy growth to a Page-value plateau) is real, established physics, distinct from all of the above, and is presented (§9) together with the timescale τ*(ℓ) it requires, and its role as the only available justification for treating the system's effective Hamiltonian Ĥeff as possessing a meaningful temperature Tc, given that the axioms admit no literal external bath. A note on generality. QGCF does not require a literal discrete graph. (QGCF3) is stated as a disjunction: a discrete, graph-based realization (QGCF3a), giving the sharper results of §8.2 and §8.6.2 exactly; or a continuum realization with only a locality/metric structure (QGCF3b), giving the standard, approximately-causal Lieb-Robinson bound instead. Everything else in this document §5-§7, §8.3-§8.6.1, §9 - depends only on finite-dimensionality and unitarity (QGCF1-QGCF2), or on (QGCF4)'s boundedness/genericity, and holds identically under either branch of (QGCF3).
Note on this consolidation This document merges three previously separate pieces (A GitHub repository with numerical checks has been added) (1) The No-Chaos Theorem, now in its corrected form: ontic chaos is impossible (§5), and - after two earlier, retracted attempts (a geometric leakage estimate with the wrong sign; an entanglement-growth mechanism that conflated entropy growth with a Lyapunov exponent and depended silently on ETH) - dynamical chaos at any fixed coarse-graining scale ℓ is proven structurally impossible (§7), with level statistics introduced as the one chaos diagnostic that survives (§7.3). (2) The thermalization content that used to be misattributed to "chaos": real physics (Calabrese–Cardy growth, Page saturation), relocated here as what it actually is (§9), together with its genuine connection to the construction used elsewhere in this work via ETH. (3) New in this consolidation: the Embedded-Observer No-Go Theorem (§8), which answers a related but logically distinct question - not whether an observer sees chaos, but whether an observer confined to a proper subgraph can ever completely reconstruct the global state or evolve autonomously. This is a better-grounded reason for an embedded observer's limited picture of reality than either chaos or thermalization, and does not depend on ETH, Page's theorem, or any genericity assumption beyond an entangling (generic) boundary coupling.
Note on this consolidation This document merges three previously separate pieces (A GitHub repository with numerical checks has been added)(1) The No-Chaos Theorem, now in its corrected form: ontic chaos is impossible (§5), and - after two earlier, retracted attempts (a geometric leakage estimate with the wrong sign; an entanglement-growth mechanism that conflated entropy growth with a Lyapunov exponent and depended silently on ETH) - dynamical chaos at any fixed coarse-graining scale ℓ is proven structurally impossible (§7), with level statistics introduced as the one chaos diagnostic that survives (§7.3). (2) The thermalization content that used to be misattributed to "chaos": real physics (Calabrese–Cardy growth, Page saturation), relocated here as what it actually is (§9), together with its genuine connection to the construction used elsewhere in this work via ETH. (3) New in this consolidation: the Embedded-Observer No-Go Theorem (§8), which answers a related but logically distinct question - not whether an observer sees chaos, but whether an observer confined to a proper subgraph can ever completely reconstruct the global state or evolve autonomously. This is a better-grounded reason for an embedded observer's limited picture of reality than either chaos or thermalization, and does not depend on ETH, Page's theorem, or any genericity assumption beyond an entangling (generic) boundary coupling.