Starobinsky inflation from the SYK₆ Schwarzian on a cubic tensor network

This paper derives the Starobinsky inflationary potential from a holographic tensor network, conditional on a single physical hypothesis. The boundary theory of the {4,3,r} model is SYK₆, whose low-energy dynamics is governed by the Schwarzian effective action with coefficient α_S ≈ 0.004 (Maldacena-Stanford). Under the hypothesis that the one-loop Schwarzian determinant lifts to a bulk R² correction via the standard JT gravity embedding, the corrected Einstein-Hilbert action has R² coefficient ξ ∝ (log χ)² χ2/3. For the observed de Sitter entropy, ξ is exponentially large, placing the model deep in the Starobinsky plateau regime. The conformal transformation to Einstein frame yields V(φ) = V₀(1 − exp(−√(2/3) φ/M_Pl))² with predictions n_s ≈ 0.965, r_T ≈ 0.004, and α_s ≈ −6 × 10⁻⁴ for 57 e-folds. The hypothesis follows standard holographic reasoning but has not been derived within the model; given the hypothesis, no free parameter enters the derivation chain. To our knowledge, this is the first derivation of a specific inflationary potential from a microscopic holographic boundary theory.