There are several decision problems for certain computation models with atoms that are decidable when atoms admit certain well quasi order (WQO), and undecidable otherwise. We recall the problems and formulate few questions related to WQOs.

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# Tag Archives: Freisse class

# Color-preserving automorphisms in Fraisse classes (new version)

Again, a question closely related to a characterization of *standard atoms* (not to be confused with standard alphabets:). The question is a refinement of a question posted in Automorphisms vs color-preserving automorphisms in Fraisse classes, which has been answered negatively (see the recent post The colored open question closed).

# Automorphisms vs color-preserving automorphisms in Fraisse classes

Here is a question closely related to a characterization of *standard atoms* (not to be confused with standard alphabets:). It asks whether a bound on the number of automorphisms is equivalent to a bound on the numer of color-preserving automorphisms, in every Fraisse class of finite relational structures.