The degree-four coefficient two fifths #
The terminal core has at most 12 β₁ / 5 edges. Gaussian vertex ordering crosses at most
one sixth of those edges, plus an arbitrarily small linear error. Expanding the blocks adds
only 4 log₂ |V| + 4, giving LayoutBound 4 (2/5).
Layouts in maximum degree four. This supplies the coefficient for ternary circuits.