Cubic incompleteness: Hilbert's tenth problem begins at degree three

We present a preliminary result addressing a long-standing open question: Are cubic Diophantine equations undecidable?} We answer in the affirmative. By encoding G\"odel's first incompleteness theorem via a Fibonacc-based G\"oodel numbering and the Zeckendorf representation, we reduce the arithmetic complexity sufficiently to construct an explicit \emph{cubic Diophantine equation} whose solvability is independent of a model provided by \emph{Peano axioms}. We present three results. First, a commonsense argument that relies on an unjustified generalization by necessity. Second, a constructive procedure that, given any Turing machine $M$, produces a cubic polynomial $Q_M(\vec{u}) \in \mathbb{Z}[\vec{u}]$ of total degree at most $3$, such that the equation $Q_M(\vec{u}) = 0$ has a solution in $\mathbb{N}^k$ if and only if $M$ halts on empty input. Third, we formalize a thesis concerning bounds.