A New Upper Bound for the Turán Density of the Tetrahedron

We prove that the Turán density of the tetrahedron $K_4^{(3)}$ satisfies $π(K_4^{(3)}) \le 312372062889819/560000000000000 < 0.557808$, improving Baber's upper bound of $0.5615$ and closing about $62\%$ of the gap to the conjectured value $5/9$. The proof uses an exact seven-vertex flag-algebra cert