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Equation 80 · Part 6 · The Bend an Elevator Cannot Fake

subscript

Γ0i0=∂iln⁡U=ϕ,i\Gamma^0_{0i} = \partial_i \ln U = \phi_{,i}
subscript

What this part means

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.

Its job in the formula

A subscript distinguishes a version, component, step, or member of a quantity. It does not automatically mean multiplication.

The passage around this formula

What must therefore vanish, identically, is not the slope but the correctly defined curvature-frame component built from it. For any static metric of the form ds2s^2 = -U(x\mathbf x)^2\,dx02x_0^2 + δij\delta_{ij}\,dxix^i dxjx^j — flat spatial slices, all the position dependence carried by U — the only nonzero Christoffel symbols are Γ0i0\Gamma^0_{0i} = ∂i\partial_i ln⁡\ln U = ϕ,i\phi_{,i} and Γ00i\Gamma^i_{00} = U2U^2ϕ,i\phi_{,i} , both following directly from the metric’s definition. Substituting into the Riemann tensor’s defining combination for the mixed component RiR^i{}_{0j0} , every term built from purely spatial Christoffels vanishes because the spatial slices are exactly flat, and the two surviving pieces are…

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Learn the underlying idea

A subscript is a label attached below a symbol. It often selects a time step, component, category, or member of a sequence.

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Sources cited in the article section

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