ihara-zeta

Compute the Ihara zeta function for graphs using the Bass-Hashimoto determinant formula.

60|13|Updated Dec 22, 2025
One-click install
npx skills add https://github.com/plurigrid/asi --skill ihara-zeta
Or copy as Structured Prompt for Agent
Please help me install this Agent Skill.
Skill: ihara-zeta
Source: https://github.com/plurigrid/asi/tree/main/skills/ihara-zeta
Command: npx skills add https://github.com/plurigrid/asi --skill ihara-zeta

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

Ihara zeta encodes non-backtracking closed walks in graphs; this Skill provides a foundation for spectral clustering, determinant formulas, and Ramanujan properties.

Core Features & Use Cases

  • Non-backtracking matrix: construct B to study graph structure.
  • Determinant formula: apply Bass-Hashimoto to ζ_G(u)^{-1}.
  • Spectral considerations: analyze eigenvalues for Ramanujan properties and clustering.

Quick Start

Given a graph G, compute the non-backtracking matrix and check the determinant-based zeta inverse.

Frequently Asked Questions about ihara-zeta

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I compute the Ihara zeta function for a graph?

The Ihara zeta function encodes non-backtracking closed walks in graphs. Construct the non-backtracking matrix B, then apply the Bass-Hashimoto determinant formula to compute ζ_G(u)^{-1}, which reveals graph structure through spectral analysis.

What are non-backtracking walks and why do they matter for graph analysis?

Non-backtracking walks exclude immediate reversals, filtering out trivial cycles. They reveal deeper structural patterns in graphs and form the foundation for spectral clustering, Ramanujan property detection, and distinguishing graph topology that standard walks obscure.

How do I extract primitive cycles from a graph using spectral methods?

Apply Möbius-based filtering to the non-backtracking matrix eigenvalues to isolate primitive cycles and eliminate redundant closed walks. This extraction supports hypothesis testing and clustering by exposing fundamental cycle structure.

Can I use Ihara zeta functions to test if a graph has Ramanujan properties?

Yes. Analyze eigenvalues of the non-backtracking matrix via the Bass-Hashimoto determinant relation. Ramanujan graphs exhibit specific spectral bounds that this analysis reveals, useful for detecting optimal expansion properties in graph clustering.

What's the relationship between the determinant formula and graph clustering?

The Bass-Hashimoto determinant formula ζ_G(u)^{-1} encodes graph connectivity through non-backtracking walks. Its spectral decomposition identifies clusters and community structure, enabling data-driven partitioning without explicit cluster assumptions.

When should I apply non-backtracking analysis instead of standard spectral graph theory?

Use non-backtracking methods when standard spectral approaches conflate short cycles with long-range structure. They excel at detecting fine-grained clustering, testing Ramanujan properties, and distinguishing community boundaries that adjacency matrices may blur.