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PreprintCC BY 4.0arXiv

Quantitative symplectic topology of Katok's examples and equivariant symplectic embeddings

Abstract

The Katok examples on S2 are induced by Randers metrics obtained by perturbing the round metric by the standard rotational Killing field: allowing a scaling factor of the round metric gives a two-parameter family of Randers metrics Fα,β, parametrised by positive real numbers (α,β). We compute the set of all (α,β)∈ (0,2+√3)2 for which D*(S2,F*α,β), the unit codisc bundle with respect to F*α,β, symplectically embeds into the round codisc bundle D*S2. This set has the structure of an infinite staircase. We also establish a dictionary between embeddings of these codisc bundles, singular A1-ellipsoid embeddings, and ℤ 2-equivariant ellipsoid embeddings, showing that these embedding problems are equivalent. Furthermore, we prove the analogous results for the ℝ P2 case and discuss a broader family of examples for which this dictionary applies.

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BibTeX
@misc{adaloglou2026quantitative,
  title = {{Quantitative symplectic topology of Katok's examples and equivariant symplectic embeddings}},
  author = {Nikolas Adaloglou and Johannes Hauber},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.35209},
  eprint = {2609.35209},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.35209},
  note = {CC BY 4.0},
}
RIS
TY  - UNPB
TI  - Quantitative symplectic topology of Katok's examples and equivariant symplectic embeddings
AU  - Nikolas Adaloglou
AU  - Johannes Hauber
PY  - 2026
DA  - 2026/09/28
PB  - arXiv
DO  - 10.48550/arxiv.2609.35209
UR  - https://arxiv.org/abs/2609.35209
AB  - The Katok examples on S^2 are induced by Randers metrics obtained by perturbing the round metric by the standard rotational Killing field: allowing a scaling factor of the round metric gives a two-parameter family of Randers metrics F_α,β, parametrised by positive real numbers (α,β). We compute the set of all (α,β)∈ (0,2+√3)^2 for which D^*(S^2,F^*_α,β), the unit codisc bundle with respect to F^*_α,β, symplectically embeds into the round codisc bundle D^*S^2. This set has the structure of an infinite staircase. We also establish a dictionary between embeddings of these codisc bundles, singular A_1-ellipsoid embeddings, and ℤ _2-equivariant ellipsoid embeddings, showing that these embedding problems are equivalent. Furthermore, we prove the analogous results for the ℝ P^2 case and discuss a broader family of examples for which this dictionary applies.
ER  -