General partial fraction decomposition conjecture for Gorenstein-symmetric rational functions

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Let P(t)=H(t)∏i=1N(1−tbi)P(t)=\frac{H(t)}{\prod_{i=1}^N(1-t^{b_i})} be a rational function with integral numerator H(t)∈Z[t]H(t)\in\mathbb Z[t] satisfying Gorenstein symmetry. Let n+1n+1 be the dimension of the support in the graded Gorenstein setting, and let kk denote the symmetry degree of P(t)P(t). For each sequence A={a1,…,an+1}A=\{a_1,\ldots,a_{n+1}\}, write r=an+1r=a_{n+1} for its main period, require ai∣ra_i\mid r, and define

kA=k+∑a∈Aa.k_A=k+\sum_{a\in A}a.

Also set

FA=1−trhcf⁡(1−tr,∏a∈A, a<r(1−ta)).F_A=\frac{1-t^r}{\operatorname{hcf}\left(1-t^r,\prod_{a\in A,\,a<r}(1-t^a)\right)}.

General partial fraction decomposition conjecture. Under these assumptions, P(t)P(t) has a unique partial fraction decomposition

P(t)=∑ANA∏a∈A(1−ta).P(t)=\sum_A\frac{N_A}{\prod_{a\in A}(1-t^a)}.

The sum is over sequences AA as above, with each aia_i dividing one of the original bjb_j. Each numerator NAN_A is an integral polynomial symmetric of degree kAk_A, and is of shortest support: it is a minimal residue modulo FAF_A, supported in an interval of length less than deg⁡FA\deg F_A centred at kA/2k_A/2. The decomposition may be restricted to quasismooth orbifolds if necessary.

This conjecture proposes a canonical decomposition of Gorenstein-symmetric Hilbert-series-type rational functions into contributions indexed by periods and their divisors. The stated uniqueness, integrality, and shortest-support properties are the substantive points; the source does not provide a resolution status.

References

Primary source

Anita Buckley, Miles Reid and Shengtian Zhou, “Ice cream and orbifold Riemann-Roch”, arXiv:1208.0457 (2012).

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