PLI–Linked Co–Evolution of c(t) and G(t) and Early– 7D 2t Universe Constraints

Starting from the world–ensemble relation c3(t) = 2 G(t) MU H(t) motivated in the
Janus/PLI programme , we derive the co–evolution law ˙G/G = 3 ˙c/c − ˙H/H and propagate it through BBN, recombination, and late–time bounds. Two regimes emerge: (i) a PLI track with c(t) ∝ H1/3(t) giving ˙G/G = 0
at all epochs; (ii) off–track solutions that are bounded by current BBN/CMB/LLR constraints
on ˙G/G and by α variation limits . We quantify the allowed late–time drift and
revisit the baryogenesis sign implied by ˙c/c.