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math.LO2026
Embeddings, ultrapowers and direct powers
Pedro Teixeira Yago
We study when embeddings lift from structures to their ultrapowers, and when an ultrapower embeds into its direct power. We offer a refinement of Blass's theorem on the Rudin-Keisl…
math.LO2026
Direct powers, ultrapowers and cumulative powers
Pedro Teixeira Yago
In this paper we investigate cumulative direct powers of functions on structures, or cumulative powers, and study their properties. Particularly, we show how they extend the preser…