Ray Time Theory (RTT) v2.6: Trace-Coupled Scalar Sector, Barotropic-Fluid Closure, and a Minimal-Canonical No-Go Theorem

Title: Ray Time Theory (RTT) v2.6: Trace-Coupled Scalar Sector, Barotropic-Fluid Closure, and a Minimal-Canonical No-Go Theorem Version v2.6 Update: This release reframes Ray Time Theory as a reality-strict scalar-tensor constraint paper. It does not claim a closed cosmological theory, Euclid validation, Hubble-tension resolution, dark-energy replacement,heat-death dimensional unspooling, or standalone dark-matter replacement. The retained mathematical sector is a trace-coupled canonical scalar trial action. Direct scalar variation derives the effective-mass relation m2 eff = m2 0 + βTvis M2 ∗ + βdTdark M2 ∗ , which is strong for the stated trial action and conditional for RTT. Radiation trace cancellation remains exact for an ideal conformal radiation fluid. The main positive closure result is a specified isentropic barotropic perfect-fluid metric variation. For a branch with Lb =−ρ(n,s), fixed entropy per particle, and fixed particle-current variation, the trace-coupling stress tensor is derived as Ttr,b µν =−fbTbgµν + fbn ∂Tb ∂n s (gµν + uµuν), with fb = βχ2/(2M2 ∗ ). This closes the trace-coupling metric variation for the specified idealized fluid branch. It does not close full baryonic astrophysical matter. The main negative result is a minimal-canonical no-go theorem. Flat rotation curves require ρeff ∝r−2. A static spherical minimal massless canonical scalar exterior gives gradient energy density ρχ ∝r−4. Therefore that structural class is excluded as a standalone dark-matter replacement under the tested assumptions. This result does not exclude screened scalar models, noncanonical kinetic structures, MOND-like modifications, or models with a separate dark-matter sector; those evade the theorem by changing the assumptions and must be audited as new actions. The dark-sector decoupling condition remains an open gateway. A viable baryon-dominated trigger requires Rd(z,T) ≪1, where Rd is the ratio of dark-sector trace forcing to baryonic trace forcing. This must be derived from a protective symmetry or thermal decoupling mechanism rather than assumed. Files Included: main v260.pdf main v260.tex rtt v260 symbolic audit.py rtt v260 nogo boundary.png rtt v260 symbolic audit results.json RTT v2 6 THEORETICAL VIABILITY MATRIX.md Recommended Claim Level RTT v2.6 should be described as a constraint paper and scalar-tensor audit artifact. It preserves closed scalar effective-mass algebra and a specified barotropic-fluid metric-variation branch, while excluding the static spherical minimal-canonical scalar as a standalone dark-matter replacement under the stated assumptions. *ORCID: 0009-0002-0409-2515. Version record: 10.5281/zenodo.20301769. Concept record: 10.5281/zenodo.20244131.