Outputs (4)

Embedding spheres in knot traces (2021)
Journal Article
Feller, P., Miller, A. N., Nagel, M., Orson, P., Powell, M., & Ray, A. (2021). Embedding spheres in knot traces. Compositio Mathematica, 157(10), 2242-2279. https://doi.org/10.1112/s0010437x21007508

The trace of the n-framed surgery on a knot in S3 is a 4-manifold homotopy equivalent to the 2-sphere. We characterise when a generator of the second homotopy group of such a manifold can be realised by a locally flat embedded 2-sphere whose compleme... Read More about Embedding spheres in knot traces.

Characterisation of homotopy ribbon discs (2021)
Journal Article
Conway, A., & Powell, M. (2021). Characterisation of homotopy ribbon discs. Advances in Mathematics, 391, Article 107960. https://doi.org/10.1016/j.aim.2021.107960

Let Γ be either the infinite cyclic group Z or the Baumslag-Solitar group Zn Z[ 1 2 ]. Let K be a slice knot admitting a slice disc D in the 4-ball whose exterior has fundamental group Γ. We classify the Γ-homotopy ribbon slice discs for K up to topo... Read More about Characterisation of homotopy ribbon discs.

Two-solvable and two-bipolar knots with large four-genera (2021)
Journal Article
Cha, J. C., Miller, A. N., & Powell, M. (2021). Two-solvable and two-bipolar knots with large four-genera. Mathematical Research Letters, 28(2), 331-382. https://doi.org/10.4310/mrl.2021.v28.n2.a2

For every integer g, we construct a 2-solvable and 2-bipolar knot whose topological 4-genus is greater than g. Note that 2-solvable knots are in particular algebraically slice and have vanishing Casson–Gordon obstructions. Similarly all known smooth... Read More about Two-solvable and two-bipolar knots with large four-genera.

Doubly slice knots and metabelian obstructions (2021)
Journal Article
Orson, P., & Powell, M. (2022). Doubly slice knots and metabelian obstructions. Journal of Topology and Analysis, 14(4), 847-873. https://doi.org/10.1142/s1793525321500229

An n-dimensional knot Sn⊂Sn+2 is called doubly slice if it occurs as the cross section of some unknotted (n+1)-dimensional knot. For every n it is unknown which knots are doubly slice, and this remains one of the biggest unsolved problems in high-dim... Read More about Doubly slice knots and metabelian obstructions.