Sandra Albrechtsen

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20242026

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math.CO2025

Excluding $K_{2, t}$ as a fat minor

Sandra Albrechtsen, Marc Distel, Agelos Georgakopoulos

We prove that for every $t \in N$ , the graph $K_{2, t}$ satisfies the fat minor conjecture of Georgakopoulos and Papasoglu: for every $K \in N$ there exist $M,A\in…

math.CO2025

Counterexample to the conjectured coarse grid theorem

Sandra Albrechtsen, James Davies

We show that for every $M, A, n \in N$ there exists a graph $G$ that does not contain the $(154 \times 154)$ -grid as a $3$ -fat minor and is not $(M, A)$ -quasi-isometric to a g…

math.CO2025

A coarse Halin Grid Theorem with applications to quasi-transitive, locally finite graphs

Sandra Albrechtsen, Matthias Hamann

We prove a coarse version of Halin's Grid Theorem: Every one-ended, locally finite graph that contains the disjoint union of infinitely many rays as an asymptotic minor also contai…

Excluding K2,t​ as a fat minor

Counterexample to the conjectured coarse grid theorem

A coarse Halin Grid Theorem with applications to quasi-transitive, locally finite graphs

Excluding $K_{2, t}$ as a fat minor