Distinct degrees and homogeneous sets

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• Laurentiu Ploscaru, University of Birmingham
• Thursday 17 March 2022, 15:00-16:00
• Poynting Large Lecture Theatre, additional zoom link: https://bham-ac-uk.zoom.us/j/88168768618.

If you have a question about this talk, please contact Eoin Long.

In this talk I will discuss some recent work examining the extremal relationship between two well-studied graph parameters: the order of the largest homogeneous set in a graph G and the maximal number of distinct degrees appearing in an induced subgraph of G, denoted respectively by hom (G) and f(G).

Our main theorem improves estimates due to Bukh and Sudakov and to Narayanan and Tomon and shows that if G is an n-vertex graph with hom (G) at least n^1/2 then f(G) > ( n / hom (G) )^{1 – o(1)}. The bound here is sharp up to the o(1)-term, and asymptotically solves a conjecture of Narayanan and Tomon. In particular, this implies that max { hom (G), f(G) } > n^{1/2 -o(1)} for any n-vertex graph G, which is also sharp.

The relationship between these parameters changes when hom (G) < n^1/2. I hope to discuss the suspected relationship in this other region, along with supporting results. Joint work with Eoin Long.

This talk is part of the Combinatorics and Probability seminar series.

This talk is included in these lists:

• Combinatorics and Probability seminar
• Poynting Large Lecture Theatre, additional zoom link: https://bham-ac-uk.zoom.us/j/88168768618
• School of Mathematics events

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