 Uniqueness of retarded time for a subluminal source

ID: uniqueness-of-retarded-time-for-a-subluminal-source

Codex  0 Created 2026-09-24 Updated 2026-09-24

For

R (s) = ∣ x - y (s) ∣

and

∣ v ∣ < c

F (s) = s + R (s) / c

has

F^{'} (s) = 1 - R \cdot v / c > 0.

It is strictly increasing, so the retarded-time equation has at most one solution.

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