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PreprintarXiv licencearXiv

Selflessness, MIF and opposition in groups acting on exotic buildings

Abstract

We prove that groups acting freely and cocompactly on (possibly exotic) affine buildings of type Ã2 and C̃2 are mixed-identity free and have selfless reduced C*-algebras. These results follow from a strong form of ping-pong dynamics that we call 'transversal contractivity'. Our main geometric result regards domesticity properties of elements in the associated polygons at infinity: we prove that, in our context, the opposite geometry of a hyperbolic element is topologically large.

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BibTeX
@misc{bars2026selflessness,
  title = {{Selflessness, MIF and opposition in groups acting on exotic buildings}},
  author = {Corentin Le Bars and Elyasheev Leibtag and Itamar Vigdorovich},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.17129},
  eprint = {2609.17129},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.17129},
}
RIS
TY  - UNPB
TI  - Selflessness, MIF and opposition in groups acting on exotic buildings
AU  - Corentin Le Bars
AU  - Elyasheev Leibtag
AU  - Itamar Vigdorovich
PY  - 2026
DA  - 2026/09/15
PB  - arXiv
DO  - 10.48550/arxiv.2609.17129
UR  - https://arxiv.org/abs/2609.17129
AB  - We prove that groups acting freely and cocompactly on (possibly exotic) affine buildings of type Ã_2 and C̃_2 are mixed-identity free and have selfless reduced C^*-algebras. These results follow from a strong form of ping-pong dynamics that we call 'transversal contractivity'. Our main geometric result regards domesticity properties of elements in the associated polygons at infinity: we prove that, in our context, the opposite geometry of a hyperbolic element is topologically large.
ER  -