Paper IV visual guide · Visual 10 of 26 · BELL PARTITIONS

The reciprocal order is a polynomial

Traditional monograph: Theorem 7.2 (p. 14), Corollary 7.7 (p. 16).

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Let \(r\) vary instead of fixing the reciprocal power. Since

\[ \Delta_N(w)^{-r}=\exp\!\left(r\sum_{m\ge1}\kappa_{N,m}\frac{w^m}{m}\right), \]

the coefficient of \(w^n\) is a polynomial of degree \(n\) in \(r\). Bell polynomials collect the possible ways logarithmic terms contribute total degree \(n\).

Three partition types contribute the cubic, quadratic and linear terms of the reciprocal-order polynomial.
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Each row names a partition type, gives its logarithmic contribution, and gives the resulting term after the plate’s factorial normalization. Three singleton pieces produce the cubic term, a pair and singleton produce the quadratic term, and a single triple produces the linear term. The Bell-polynomial identity underneath combines the three rows.

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Partition contributions
Partition typeLogarithmic termNormalized contribution
three singletons\(r^3\kappa_1^3\)\(15r^3\)
one pair, one singleton\(3r^2\kappa_1\kappa_2\)\(30r^2\)
one triple\(2r\kappa_3\)\(16r\)
\[P_{2,3}(r)=\frac{6!}{3!}\,B_3(r\kappa_1,r\kappa_2,2r\kappa_3)\]

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For \(N=2\), the first three logarithmic coefficients are

\[ \kappa_1=\frac12,\qquad\kappa_2=\frac16,\qquad\kappa_3=\frac1{15}. \]

The third Bell polynomial is \(B_3(x_1,x_2,x_3)=x_1^3+3x_1x_2+x_3\). Substituting \(x_1=r\kappa_1\), \(x_2=r\kappa_2\), \(x_3=2r\kappa_3\) and multiplying by \(6!/3!\) gives

\[ P_{2,3}(r)=15r^3+30r^2+16r. \]

At \(r=1\) this is \(61\). At \(r=2\) it is \(272\). At \(r=0\) it vanishes, as every positive-index reciprocal coefficient must.

The leading term has a simple source

Only \(n\) copies of the linear logarithmic term can contribute \(r^n w^n\). Therefore

\[ [r^n]P_{N,n}(r)=\frac{(Nn)!}{n!(N!)^n}. \]

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The polynomial parameter records how many logarithmic pieces are combined. It is not a numerical interpolation in the reciprocal order.

Evidence note from the source edition

The partition plate is a finite combinatorial expansion. The exact tests verify the leading coefficient and parameter polynomial through block index six for five orders.

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