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20172025
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math.CO2025

Non-dissective coverings by planks

Andrey Kupavskii, Janos Pach

A plank is the part of space between two parallel planes. The following open problem, posed 45 years ago, can be viwed as the converse of Tarski's plank problem (Bang's theorem): I…

math.CO2025

A complete -intersection theorem for families of spanning trees

Elizaveta Iarovikova, Andrey Kupavskii

Let denote the set of all labelled spanning trees of . A family is -intersecting if for all the trees…

math.CO2025

The Erdős-Rado Sunflower Problem for Vector Spaces

Ferdinand Ihringer, Andrey Kupavskii

The famous Erdős-Rado sunflower conjecture suggests that an -sun\-flower-free family of -element sets has size at most for some absolute constant . In this note,…

math.CO2025

The Hajnal--Rothschild problem

Peter Frankl, Andrey Kupavskii

For a family define as the largest for which there exist such that for we have . Wha…

math.CO2025

Intersecting Families of Spanning Trees

Peter Frankl, Glenn Hurlbert, Ferdinand Ihringer +4

A family of spanning trees of the complete graph on vertices is \emph{-intersecting} if any two members have a forest on edges in common. We prove an…

math.CO2024

Linear dependencies, polynomial factors in the Duke--Erd\H os forbidden sunflower problem

Andrey Kupavskii, Fedor Noskov

We call a family of sets a \textit{sunflower with petals} if, for any distinct , one has . The set $…