3 papers
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…
cs.LO2026
Importing soundness and completeness in modal logics
Pedro Teixeira yago
We develop general strategies for transferring soundness and completeness from more expressive modal languages to less expressive ones, unifying several existing notions of operato…
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…