Gated exciton fluids V: three dimensions - what the T-duality, holography and projection analogies do and do not give, measured

Fifth paper of the gated-exciton line (I: 10.5281/zenodo.23294615; II: 10.5281/zenodo.23297479; III: 10.5281/zenodo.23298292; IV: 10.5281/zenodo.23302787). It asks whether ideas borrowed from string theory (lifting to 8 or 24 dimensions, holography, projection, T-duality) help with the three-dimensional node-arrangement problem. Known fact first: in R^3 no configuration is universally optimal, because the Poisson dual of FCC is BCC and the two exchange roles at the self-dual Gaussian parameter alpha=pi. Two pre-registered rounds of experiments follow.

Round 1: among 3D Bravais lattices the minimiser is always FCC or BCC (29/29 kernel points; Gaussian crossover a*=pi to 3e-14); random-restart searches over non-Bravais cells with up to 16 points find nothing below min(FCC, BCC, HCP, A15) in 9,860 restarts; on S^3, where the 600-cell is a proved optimum, a local optimiser reaches it for long-range and soft kernels but not for stiffer Gaussians; along the Bain path the self-dual (isodual) lattice at alpha=pi is the energy maximum between the two degenerate minima, so the T-duality analogy explains why no 3D universal optimum exists rather than pointing to one.

Round 2 (negative throughout): F1, an alpha-homotopy from a soft kernel, reaches the proved 600-cell in 0, 0 and 6 of 50 seeds at a=1, 2, 4, while plain restarts at equal compute reach it in 50/50 at a=4; by the registered stop rule our 3D searches are declared unreliable. T2: Gaussian mixtures straddling the self-dual point give nothing below FCC/BCC/HCP in 5,100 restarts. T1: a search for formally self-dual configurations accepts nothing, but its objective cannot tell the known one (diamond) from configurations 1e-3 away, so the negative is uninformative. H1: the two-point linear-programming code failed its own one-dimensional sanity gate (under an admissibility tolerance fixed in code, not registered) and was not run in d=3. Deviations from the registrations are listed; two adversarial reviews and their resolutions are in the source archive.

Version 2 adds H1': a literature check found that H1's question at alpha=pi is already answered (Cohn and de Courcy-Ireland, arXiv:1603.09684, Table 1.1: two-point bound 0.2232 against a record of 0.2315 in d=3). An attempt at rigorous certificates was abandoned in development; a re-registered numerical, not certified run with the same LP code reproduces the published d=1, 2, 3 values at alpha=pi within the registered windows (d=1 and d=3 to the printed 8 digits) and gives gaps of 0.48%, 6.7% and 21.6% below the best lattice in d=3 at alpha=2, 4, 8: numerically, at polynomial degree up to 40, two-point bounds do not settle the 3D question at any alpha tested. A hostile review found no blocking item; its corrections are applied.

Everything is small-scale, classical and single-engine; nothing uses the unrefereed planar lattice theorem; no claim about excitons. Written by an AI system; checked by independent instances; not refereed.