Cioabă, Desai and Tait's spectral Turán containment conjecture

Let FF be a graph. Write EX(n,F)\operatorname{EX}(n,F) for the family of FF-free graphs attaining the extremal number, and let SPEX(n,F)\operatorname{SPEX}(n,F) denote the family of FF-free graphs attaining the maximum spectral radius. A graph family is Turán graphs plus O(1)O(1) edges if each of its graphs can be obtained from the appropriate Turán graph by adding O(1)O(1) edges. Cioabă, Desai and Tait's conjecture. If the graphs in EX(n,F)\operatorname{EX}(n,F) are Turán graphs plus O(1)O(1) edges, then, for sufficiently large nn,

SPEX(n,F)EX(n,F).\operatorname{SPEX}(n,F)\subseteq\operatorname{EX}(n,F).

This proposes a general condition under which spectral extremal graphs are also extremal in the ordinary Turán problem; the source gives examples where the containment is known, but does not state a resolution of the conjecture.

Sources & referencesView supporting material

Primary source

Lele Liu and Bo Ning, “Spectral Turán-type problems on sparse spanning graphs”, arXiv:2307.14629 (2023).

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