Homological spectral graph theory and weighted cycle counting

Abstract

Twisting a finite graph by its homology characters produces families of generally non- Hermitian weighted vertex and edge adjacency matrices. We show that these families are organized by the canonical 2-torsion character and, when it exists, a period character. The canonical character θ translates every complex character to an anti-isospectral partner, for every positive directed weight. On the unitary character torus, the untwisted matrices maximize spectral radius strictly apart from topologically forced exceptions; for edge adjacency, the only possible additional maximizer is the period character η. For symmetric weights, these results locate the two outer spectral edges of maximal-abelian and periodic Bloch families. Fourier inversion of twisted edge traces then yields weighted circuit and prime-cycle formulas in integral and finite-quotient homology classes, with θ and η, when present, governing the resulting parity effects. Thus spectral antisymmetry, spectral-edge extremality, and weighted cycle counting arise from the same homological structure.

Substantially revised and expanded version, with a new title; 74 pages, 6 figures. The results are extended to positive directed weights, and the period character is introduced to complete the spectral-radius extremality classification for twisted edge adjacency