The de Sitter solution shows that accelerated expansion can be a property of empty geometry rather than a consequence of matter content. This note identifies the projective analogue of that statement inside the Heisenberg spectral admissibility cascade. The result does not claim that Heisenberg balls grow exponentially. They do not: by the Bass–Guivarc'h formula their growth is polynomial of degree four. The exponential component survives only after replacing endpoint counting by projectively distinguishable trajectory counting. We define a hierarchy of trajectory distinguishability notions and show that any endpoint-based definition collapses to polynomial growth. The canonical O12-compatible residual channel is b-only and therefore bounded by the non-backtracking abelian-shadow entropy. For a generic probe, the residual profile separates the b-sequences on the pre-saturation window. Consequently, the distinguishable-history count is the Pell count \ Nb (n) =2Nb (n-1) +Nb (n-2), hb=₍1n Nb (n) = (1+2). \ The equality is witnessed exactly on the sampled histories of a multi-prime campaign (q\29, 61, 101, 211\) and the genericity condition on the probe is proved to fail only on a finite union of proper real-algebraic hypersurfaces. The full-history Gabor channel is strictly compressive: a geodesic-death mechanism confines nonzero symbols to trajectories whose abelian shadow is an outward geodesic, and for a generic probe its distinguishable-history count is bracketed between 2ⁿ and 2^n+2 on the pre-saturation window, so the channel has positive and exactly pinned symbolic entropy 2, strictly below the canonical rate. Its finite-horizon compression profile is retained as the candidate input for an evolving effective equation of state. The cosmological conclusion is structural: accelerated expansion, if inherited by the cosmological branch, is not driven by exponential growth of Heisenberg states but by exponential branching of projectively distinguishable histories.
Jérôme Beau (2026) studied this question.