The energy at almost every time is a time integral from the reference time #
Fix a reference time τ₀ of the mollified equation (CIV.ae_isReferenceTime_mollifySlice) at
which the mollified slice lies below M. For each spatial point x, the function
L(x, τ) = q_ε(x, τ₀) + ∫_{τ₀}^τ H(x, r) dr is absolutely continuous in τ and agrees with
q_ε(x, τ) at almost every τ for almost every x (this is the time representative of the
manuscript, the sentence after eq:aniso:comparison:mollified); at τ₀ it is the mollified slice
itself. The chain rule for the comparison profile G along L - Ψ_σ then gives, for almost every
later time τ and almost every x,
G(q_ε(x, τ) - Ψ_σ(x, τ)) = ∫_{τ₀}^τ G'(q_ε - Ψ_σ)(x, s) (H(x, s) - ∂_τΨ_σ) ds,
since G(q_ε - Ψ_σ) vanishes at τ₀.
The time integrability of the right side of the mollified equation at a fixed point.
The energy density along the time representative, at one spatial point.
The energy density at almost every later time, for almost every point, is the time
integral from the reference time τ₀ of G'(q_ε - Ψ_σ)(H - ∂_τΨ_σ).