English

Higher amalgamation in $\mathrm{ACFA}^{+}$

Logic 2026-01-09 v1

Abstract

We show two results on higher amalgamation in the theory ACFA+\mathrm{ACFA}^{+}, the model companion of the theory of difference fields with an additive character (added as a continuous logic predicate) on the fixed field in characteristic 0. On one hand, we show that the non-trivial condition for 3-amalgamation established in a preceding paper is not sufficient for 4-amalgamation. On the other hand, we show that when working over substructures whose Lσ\mathcal{L}_{\sigma}-reduct is a model of ACFA\mathrm{ACFA}, nn-amalgamation holds for all n3n\geq 3.

Cite

@article{arxiv.2601.05096,
  title  = {Higher amalgamation in $\mathrm{ACFA}^{+}$},
  author = {Stefan Marian Ludwig},
  journal= {arXiv preprint arXiv:2601.05096},
  year   = {2026}
}

Comments

23 pages without bibliography, comments welcome

R2 v1 2026-07-01T08:56:28.452Z