Tag

preservation theorem

1 resource tagged “preservation theorem” across the knowledge library.

1 item

Guide6 Aug 2026Preservation Theorems: Horn, Universal and Positive SentencesThe preservation theorems: Łoś–Tarski for substructures, Lyndon for homomorphisms, Keisler–Galvin for reduced products, Chang–Łoś–Suszko for unions of chains, and their relationship to Birkhoff's theorem.5 min readRead More