Sam Mattheus

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20242026

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math.CO2026

An improved algebraic construction for Ramsey numbers

Ferdinand Ihringer, Sam Mattheus

We provide an explicit algebraic construction showing that, uniformly for integers $3 \leq s \leq t$ , as $t \to \infty$ , \[ R( s,t ) \geq t^{(1-o(1)) \log s / \log(\log s + 1) }. \…

math.GR2026

There are no sharply transitive subsets of $SL (2, q)$ for $q \geq 13$

John Bamberg, Sam Mattheus

It was known at least to L.E. Dickson in 1901 that $SL (2, q)$ , in its natural action on $F_{q}^{2} ∖ {0}$ , has a sharply transitive subgroup only when $q\in\{2…

math.CO2026

A note on the classification of classical distance-regular graphs of negative type and the non-existence of hemisystems

Sam Adriaensen, Jan De Beule, Jozefien D'haeseleer +1

DISCLAIMER: Due to an error in the literature, we cannot be sure that the conclusions drawn in this paper are correct. The goal of this note is to connect some interesting results…

An improved algebraic construction for Ramsey numbers

There are no sharply transitive subsets of SL(2,q) for q≥13

A note on the classification of classical distance-regular graphs of negative type and the non-existence of hemisystems

There are no sharply transitive subsets of $SL (2, q)$ for $q \geq 13$