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Shadow Theory

Section 8 9 October 2026

Earlier receivers during every later operation

Reading position 9 of 16

8 Earlier receivers during every later operation

Once receiver zz has been written, the prescribed parent has

H(τ)=HA(z)⊗I+I⊗Hrest(τ). H(\tau)=H_A(z)\otimes I+I\otimes H_{\rm rest}(\tau). (8.1)

The rest includes all later scratch/archive operations, all unused receivers, used and unused reset modes, earlier records, and retained reference systems. No bath is sampled or removed. The actual pointwise receiver velocity can depend on that rest. The following bound controls it through the full wave.

Define

Fch(Θ)=100Θ(A+1)2e−A2/12,Feh(Θ)=720G(hgΘ+12BAΘ2)+5400(hg2Θ+hgBAΘ2+13BA2Θ3).\begin{align}F_{\rm ch}(\Theta) &=100\Theta(A+1)^2e^{-A^2/12},\tag{8.2}\\ F_{\rm eh}(\Theta) &=720G\left(h_g\Theta+\tfrac12B_A\Theta^2\right) \notag\\ &\quad+5400\left(h_g^2\Theta+h_gB_A\Theta^2+ \tfrac13B_A^2\Theta^3\right). \tag{8.3}\end{align}
Proposition 8.1 (Held-region current with arbitrary spectators)

Under (8.1), the actual probability that a written receiver crosses either physical boundary z=±A/2z=\pm A/2 during an interval of length at most Θ\Theta is at most C[Fch(Θ)+Feh(Θ)]C[F_{\rm ch}(\Theta)+F_{\rm eh}(\Theta)]. The constants do not acquire a factor depending on the number of spectator coordinates.

Proof

View the full wave as a function of zz with values in the rest Hilbert space. Every zz-independent unitary preserves both ∥F(z)∥\|F(z)\| and ∥∂zF(z)∥\|\partial_zF(z)\|. In particular

∫rest∣jz(z,qrest)∣ dqrest≤2∥F(z)∥∥∂zF(z)∥ \int_{\rm rest}|j_z(z,q_{\rm rest})|\,dq_{\rm rest} \leq2\|F(z)\|\|\partial_zF(z)\| (8.4)

has a spectator-invariant upper bound. This uses full Hilbert slice norms, not a putative pure phase for a reduced mixed state.

Propagate each final comparison branch with its own centered harmonic well in zz and exactly the same UrestU_{\rm rest} as the true evolution. Its slice norms may equivalently be evaluated with the original harmonic spectator evolution of the two-coordinate Gaussian. The strict tube (6.3) is then available for the entire hold. At each boundary the branch slice density is at most 12e−A2/12\frac12e^{-A^2/12}, because its nearer center is at least .45A.45A away and its variance is at most 1.11.1. Conditioning the joint Gaussian on zz bounds its derivative slice norm by 10(A+1)10(A+1) times its amplitude slice norm: the normal displacement is at most 31A/2031A/20, the normal variance is at least .9.9, and the conditional tangential derivative second moment is bounded using ∥Σ−1∥≤10/9\|\Sigma^{-1}\|\leq10/9, ∥B∥≤.2\|B\|\leq.2, and ∣p∣≤A/20|p|\leq A/20. The elementary conditional normal formula gives a constant smaller than 3(A+1)3(A+1); the displayed 1010 is an outward reserve. Coherent summation in (8.4) therefore bounds the two boundary currents by 40(A+1)e−A2/1240(A+1)e^{-A^2/12} per unit time, which is below the coefficient in (8.2).

For the true-minus-comparison error use the partial positive graph Kz=HA(z)+cK_z=H_A(z)+c. It commutes with every rest unitary. At the gate endpoint its norm is bounded by hgh_g, because KzK_z is dominated in norm by the commuting positive full graph HA(z)+Ho(x)+cH_A(z)+H_{\rm o}(x)+c. The forcing is Ds(z)D_s(z) times each comparison branch. Its KzK_z norm also commutes through UrestU_{\rm rest} and is no larger than the full positive Gaussian graph norm already bounded by BAB_A. Duhamel in this static partial graph gives

∥KzE(t)∥≤hg+tBA. \|K_zE(t)\|\leq h_g+tB_A.

The one-coordinate form of (6.8) gives receiver words through degree two bounded by 15(hg+tBA)15(h_g+tB_A); the comparison receiver words are bounded by GG. No spectator derivative is taken.

At one fixed plane the Hilbert-valued trace and current expansion used above give 24KG+12K224KG+12K^2 for K=15(hg+tBA)K=15(h_g+tB_A). Two planes give 48KG+24K248KG+24K^2. Integrating this polynomial in tt yields exactly (8.3). Coarea, equivariance and the original complete cap finish the bound. No cap conditional on the receiver's selected sign is used.

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