##### Department of Mathematics,

University of California San Diego

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### Combinatorics Seminar (Math 269)

## Sam Spiro

## Sidorenko Hypergraphs and Random Tur\'an Numbers

##### Abstract:

Let $\mathrm{ex}(G_{n,p}^r,F)$ denote the maximum number of edges in an $F$-free subgraph of the random $r$-uniform hypergraph $G_{n,p}^r$. Following recent work of Conlon, Lee, and Sidorenko, we prove non-trivial lower bounds on $\mathrm{ex}(G_{n,p}^r,F)$ whenever $F$ is not Sidorenko. This connection between Sidorenko's conjecture and random Tur\'an problems gives new lower bounds on $\mathrm{ex}(G_{n,p}^r,F)$ whenever $F$ is not Sidorenko, and further allows us to bound how ``far'' from Sidorenko an $r$-graph $F$ is whenever upper bounds for $\mathrm{ex}(G_{n,p}^r,F)$ are known. This is joint work with Jiaxi Nie.

Host: Brendon Rhoades

### January 9, 2024

### 2:00 PM

APM 7321

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