The twisted convolution identity and ghost r-SICs from finite quantum dilogarithms
Abstract
Radchenko and Wheeler (RW) recently proved a finite pentagon relation for real quadratic special values of the modular quantum dilogarithm and used it to establish the rank-$1$ twisted convolution identity conjectured by the current authors. RW gave an explicit argument in the principal case and remarked that their proof holds for all rank-$1$ admissible tuples. We extend their proof to all rank-r admissible tuples and provide an explicit dictionary between the modular quantum dilogarithm and the Shintani-Faddeev modular cocycle conventions in the respective papers. Thus, we establish that, if d,r are positive integers such that r<(d−1)/2 and (d2−1)/(r(d−r)) ∈ ℤ, then there exist ghost r-SICs: i.e., configurations of d2 rank-r subspaces in ℂd that satisfy a non-Hermitian equichordal condition. Under the Stark conjecture, these configurations are Galois conjugate to Hermitian equichordal configurations called r-SICs (or rank-r SIC-POVMs).
Related
- Real quadratic fields and finite quantum dilogarithms I
- Quantum gates from the middle convolution of twisted Burau representations
- Approximate Uniformity in Finite Convolution Models
- Twisted Deligne modules and abelian varieties over finite fields
- Classification of finite-dimensional Nichols algebras of rank two in twisted Yetter--Drinfeld categories
BibTeX
@misc{appleby2026twisted,
title = {{The twisted convolution identity and ghost $r$-SICs from finite quantum dilogarithms}},
author = {Marcus Appleby and Steven T. Flammia and Gene S. Kopp},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.39192},
eprint = {2609.39192},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.39192},
}
RIS
TY - UNPB
TI - The twisted convolution identity and ghost r-SICs from finite quantum dilogarithms
AU - Marcus Appleby
AU - Steven T. Flammia
AU - Gene S. Kopp
PY - 2026
DA - 2026/09/30
PB - arXiv
DO - 10.48550/arxiv.2609.39192
UR - https://arxiv.org/abs/2609.39192
AB - Radchenko and Wheeler (RW) recently proved a finite pentagon relation for real quadratic special values of the modular quantum dilogarithm and used it to establish the rank-$1$ twisted convolution identity conjectured by the current authors. RW gave an explicit argument in the principal case and remarked that their proof holds for all rank-$1$ admissible tuples. We extend their proof to all rank-r admissible tuples and provide an explicit dictionary between the modular quantum dilogarithm and the Shintani-Faddeev modular cocycle conventions in the respective papers. Thus, we establish that, if d,r are positive integers such that r<(d−1)/2 and (d^2−1)/(r(d−r)) ∈ ℤ, then there exist ghost r-SICs: i.e., configurations of d^2 rank-r subspaces in ℂ^d that satisfy a non-Hermitian equichordal condition. Under the Stark conjecture, these configurations are Galois conjugate to Hermitian equichordal configurations called r-SICs (or rank-r SIC-POVMs).
ER -