Self-similarity in cubic blocks of $\mathcal{R}$-operators

Cubic blocks are studied assembled from linear operators $\mathcal{R}$ acting in the tensor product of $d$ linear “spin” spaces. Such operator is associated with a linear transformation $A$ in a vector space over a field $F$ of a finite characteristic $p$, like “permutation-type” operators studied by Hietarinta. One small difference is that we do not require $A$ and, consequently, $\mathcal{R}$ to be invertible; more importantly, no relations on $\mathcal{R}$ are required of the type of Yang–Baxter or its higher analogues. It is shown that, in $d=3$ dimensions, a $p^n\times p^n\times p^n$ block decomposes into the tensor product of operators similar to the initial $\mathcal{R}$. One generalization of this involves commutative algebras over $F$ and allows to obtain, in particular, results about spin configurations determined by a four-dimensional $\mathcal{R}$. Another generalization deals with introducing Boltzmann weights for spin configurations; it turns out that there exists a non-trivial self-similarity involving Boltzmann weights as well.