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Seminar

EC Seminar: Unbalanced Zarankiewicz problem for bipartite subdivisions April 08, 2025 (04:30 PM PDT - 05:15 PM PDT)
Parent Program:
Location: SLMath: Eisenbud Auditorium, Online/Virtual
Speaker(s) Ji Zeng (Alfréd Rényi Institute of Mathematics)
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Keywords and Mathematics Subject Classification (MSC)
Primary Mathematics Subject Classification No Primary AMS MSC
Secondary Mathematics Subject Classification No Secondary AMS MSC
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Unbalanced Zarankiewicz problem for bipartite subdivisions

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For a bipartite graph $H$, its linear threshold is the smallest real number $\sigma$ such that every bipartite graph $G = (U \sqcup V, E)$ with unbalanced parts $|V| \gtrsim |U|^\sigma$ and without a copy of $H$ must have a linear number of edges $|E| \lesssim |V|$. We prove that the linear threshold of the complete bipartite subdivision graph $K_{s,t}'$ is at most $\sigma_s = 2 - 1/s$. Moreover, we show that any $\sigma < \sigma_s$ is less than the linear threshold of $K_{s,t}'$ for sufficiently large $t$ (depending on $s$ and $\sigma$). In this talk, I will discuss the proof of this result and some consequences in incidence geometry. Joint work with Lili Ködmön and Anqi Li.

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Unbalanced Zarankiewicz problem for bipartite subdivisions