Diamond lift of Hirose--Sato's formula involving the Hoffman basis
Shin-ichiro Seki
TL;DR
This work proves that Hirose–Sato's explicit Hoffman-basis expansion for a class of multiple zeta values can be derived from the drop 1 relation. By introducing the drop 1 operator $\mathcal{D}$ on the non-commutative algebra $\mathcal{H}$ and establishing the key identity $Z(w_1\tau(w_2))=Z(w_1\star w_2)$ via an induction on weight, the authors provide a new, integer-coefficient proof of the Hirose–Sato expansion. The paper also extends these ideas to the zeta-diamond framework and to finite multiple zeta values, deriving corresponding FMZV corollaries and showing the compatibility with shuffle-type structures. The results connect the drop 1 mechanism with explicit, basis-specific representations of MZVs and offer a pathway to finite-field analogues, strengthening the interplay between algebraic relations and concrete combinatorial expansions.
Abstract
In this paper, we give a new proof of Hirose--Sato's formula for the expansion of $ζ(\{2\}^{a_1-1},3,\dots,\{2\}^{a_r-1},3,\{2\}^{c-1},1,\{2\}^{b_1},\dots, 1,\{2\}^{b_s})$ in the Hoffman basis, using the drop 1 relation.
