Sharp square dimension growth via the exponential bound #
The sharp form of the square-dimension growth: it runs on the
analytic n ^ n ≤ e ^ n · n ! (one term of the Taylor series of
exp) where square_growth runs on the cruder combinatorial
n ^ n ≤ 3 ^ n · n !, and it is the sharp constant that yields the
displayed 2e of the paper.
theorem
RS.square_growth_sharp
(R : ℝ)
(hR : 0 ≤ R)
(s : ℕ)
(hs : 2 * Real.exp 1 * R < ↑s)
(S₀ :
Submodule (MonoidAlgebra ℂ (Equiv.Perm (Fin (squareDiagram s).card)))
(MonoidAlgebra ℂ (Equiv.Perm (Fin (squareDiagram s).card))))
:
(∀ (π : Equiv.Perm (Fin (squareDiagram s).card)), jtChar (squareDiagram s) π = nChar S₀ π) → R ^ s ^ 2 < ↑(nDim S₀)
Sharp square dimension growth. For a real R ≥ 0 and any
s > 2eR, every submodule of the regular module whose character
equals the JT character of the s × s square diagram has dimension
exceeding R ^ (s²).
This recovers the paper's displayed 2e: the proof runs on
n ^ n ≤ e ^ n · n !, and it is that e which appears in the
threshold. The paper makes no claim that 2e cannot be
improved.