MathDB
Draw the two graphs and find their relation

Source: 2019 Jozsef Wildt International Math Competition-W. 20

May 18, 2020
polynomialgraphgraph theory

Problem Statement

[*] Let GG be a (4,4)(4, 4) unoriented graph, 2-regulate, containing a cycle with the length 3. Find the characteristic polynomial PG(λ)P_G (\lambda) , its spectrum Spec(G)Spec (G) and draw the graph GG. [*] Let GG' be another 2-regulate graph, having its characteristic polynomial PG(λ)=λ44λ2+α,αRP_{G'} (\lambda) = \lambda^4 - 4\lambda^2 + \alpha, \alpha \in \mathbb{R}. Find the spectrum Spec(G)Spec(G') and draw the graph GG'. [*] Are the graphs GG and GG' cospectral or isomorphic?