Nonstandard combinatorial ultrafilters and a new local witness model

@misc{heil2026nonstandard,
  title = {{Nonstandard combinatorial ultrafilters and a new local witness model}},
  author = {Johannes Heil and Moritz Müller},
  howpublished = {arXiv},
  year = {2026},
  month = oct,
  doi = {10.48550/arxiv.2610.15018},
  eprint = {2610.15018},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2610.15018},
  note = {CC BY-NC-SA 4.0},
}

TY  - UNPB
TI  - Nonstandard combinatorial ultrafilters and a new local witness model
AU  - Johannes Heil
AU  - Moritz Müller
PY  - 2026
DA  - 2026/10/10
PB  - arXiv
DO  - 10.48550/arxiv.2610.15018
UR  - https://arxiv.org/abs/2610.15018
AB  - A central object in the theory of proof complexity generators is Krajicek's local witness model. We construct a new such model as a definable ultrapower using a definable version of a selective ultrafilter over a model of arithmetic. We transfer some set theory of combinatorial ultrafilters to the definable nonstandard setting.
ER  -