Minimum spectral radius conjecture for graphs with odd order and prescribed domination number

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Let n≥3n\geq3 be odd, and let Gn,⌊n2⌋\mathbb{G}_{n,\lfloor\frac{n}{2}\rfloor} denote the class of graphs on nn vertices with domination number ⌊n2⌋\lfloor\frac{n}{2}\rfloor. Let H′H' be the tree obtained from P⌊n2⌋∘K1P_{\lfloor\frac{n}{2}\rfloor}\circ K_1 by subdividing once a pendant edge on its diameter, and write H=H′H=H' as in the conjecture. Here ρ(G)\rho(G) denotes the spectral radius of a graph GG.

Minimum spectral radius conjecture. For every graph G∈Gn,⌊n2⌋G\in\mathbb{G}_{n,\lfloor\frac{n}{2}\rfloor},

ρ(G)≥ρ(H),\rho(G)\geq\rho(H),

and equality holds if and only if G≅H′G\cong H'.

The preceding even-order result identifies the minimizer as Pn/2∘K1P_{n/2}\circ K_1. The odd-order analogue is presented as not easy to prove, and no resolution is supplied in the given text.

References

Primary source

Chang Liu and Jianping Li, “The minimum spectral radius of graphs with a given domination number”, arXiv:2212.01017 (2022).

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