From an odd arity signature to a Holant dichotomy
Boning Meng, Juqiu Wang, Mingji Xia, Jiayi Zheng
TL;DR
This work advances the classification of complex-valued Holant problems on the Boolean domain by proving a dichotomy for Holant^odd, contingent on the existence of a non-trivial odd-arity signature. Central to the approach is a generalized decomposition lemma that either reduces a Holant instance to a tensor product f⊗g or places the problem in FP^NP via #EO dichotomy-guided reductions. The authors develop a robust toolkit—gadget construction with signature matrices, holographic transformations including SLOCC, polynomial interpolation, and UPF-based factorization—to realize and reduce signatures while controlling complexity. The results unify and extend prior dichotomies, provide a principled path for reductions in complex-valued Holant, and point to the remaining challenge of the even-arity irreducible case as a direction for future work with potential implications for broader counting complexity landscapes.
Abstract
\textsf{Holant} is an essential framework in the field of counting complexity. For over fifteen years, researchers have been clarifying the complexity classification for complex-valued \textsf{Holant} on the Boolean domain, a challenge that remains unresolved. In this article, we prove a complexity dichotomy for complex-valued \textsf{Holant} on Boolean domain when a non-trivial signature of odd arity exists. This dichotomy is based on the dichotomy for \textsf{\#EO}, and consequently is an $\text{FP}^\text{NP}$ vs. \#P dichotomy as well, stating that each problem is either in $\text{FP}^\text{NP}$ or \#P-hard. Furthermore, we establish a generalized version of the decomposition lemma for complex-valued \textsf{Holant} on Boolean domain. It asserts that each signature can be derived from its tensor product with other signatures, or conversely, the problem itself is in $\text{FP}^\text{NP}$. We believe that this result is a powerful method for building reductions in complex-valued \textsf{Holant}, as it is also employed as a pivotal technique in the proof of the aforementioned dichotomy in this article.
