A combinatorial proof of the extension property for partial isometries
We present a short and self-contained proof of the extension property for partial isometries of the class of all finite metric spaces.
A - finite actions and their automorphism groups.
Acyclic groups of automorphisms.
Amenable group actions on infinite graphs.
Analyse harmonique des groupes d'automorphismes d'arbres de Bruhat-Tits
Autohomeomorphism groups of spaces with unique non-isolated point
Automorphism invariants for semigroups.
Automorphisms of models of bounded arithmetic
We establish the following model-theoretic characterization of the fragment IΔ₀ + Exp + BΣ₁ of Peano arithmetic in terms of fixed points of automorphisms of models of bounded arithmetic (the fragment IΔ₀ of Peano arithmetic with induction limited to Δ₀-formulae). Theorem A. The following two conditions are equivalent for a countable model of the language of arithmetic: (a) satisfies IΔ₀ + BΣ₁ + Exp; (b) for some nontrivial automorphism j of an end extension of that satisfies IΔ₀. Here is the...
Autormorphism groups of countable highly homogeneous partially ordererd sets.