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Equation 123 · The Bit Comes Back Before the Bearing

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tG≈12.4 mst_G \approx 12.4\,\mathrm{ms}

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tGt_G

Symbol t_G

arbitrary on its own — each is anchored to a cited, checkable piece of theory, and the crossover tolerance δ∗\delta^\ast is computed, not chosen after the fact to produce a headline.

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≈

≈

Approximately equal to; the equality is not exact.

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subscript

subscript

The lower label selects a particular version, component, or indexed member of the quantity. For example, x₀ and xₜ can be values at different positions.

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What the article says around this equation

A third, more uncomfortable check is what the toy model of the previous section actually implies at the numbers already computed: tLt_L ≈\approx 3.5\,ms\mathrm{ms} , or tLt_L/β\beta ≈\approx 28.2 , for the solar-mass hole above. Taking f1f_1 = 1 as an illustrative, explicitly assumed per-quantum information content, a modest tolerance δ\delta = 0.1\,rad\mathrm{rad} (about six degrees) gives tGt_G/β\beta = 100 , so tGt_G ≈\approx 12.4\,ms\mathrm{ms} and Δ\Delta tLGt_{LG} ≈\approx +8.9\,ms\mathrm{ms} : the compass is the slower debt, as the title claims. But a coarser tolerance, δ\delta = 0.5\,rad\mathrm{rad} (about twenty-nine degrees), gives tGt_G/β\beta = 4 , so tGt_G ≈\approx 0.50\,ms\mathrm{ms} and Δ\Delta tLGt_{LG} ≈\approx…
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A third, more uncomfortable check is what the toy model of the previous section actually implies at the numbers already computed: tLt_L ≈\approx 3.5\,ms\mathrm{ms} , or tLt_L/β\beta ≈\approx 28.2 , for the solar-mass hole above. Taking f1f_1 = 1 as an illustrative, explicitly assumed per-quantum information content, a modest tolerance δ\delta = 0.1\,rad\mathrm{rad} (about six degrees) gives tGt_G/β\beta = 100 , so tGt_G ≈\approx 12.4\,ms\mathrm{ms} and Δ\Delta tLGt_{LG} ≈\approx +8.9\,ms\mathrm{ms} : the compass is the slower debt, as the title claims. But a coarser tolerance, δ\delta = 0.5\,rad\mathrm{rad} (about twenty-nine degrees), gives tGt_G/β\beta = 4 , so tGt_G ≈\approx 0.50\,ms\mathrm{ms} and Δ\Delta tLGt_{LG} ≈\approx -3.0\,ms\mathrm{ms} : under this same model, on this same hole, the compass now comes back first. The crossover, where 1/(f1f_1δ2\delta^2) = ln⁡\ln S/2π\pi , sits at δ∗\delta^\ast ≈\approx 0.188\,rad\mathrm{rad} , about eleven degrees, for this hole and this choice of f1f_1 . A fourth, trivial floor closes the set of checks: for CtC_t smaller than the input systems themselves, or for t before scrambling has had time to run at all, neither ϵL(t)\epsilon_L(t) nor Var⁡\operatorname{Var}g^\hat g meets any nontrivial bound — nothing has left yet, which is simply causality, not a result.

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