## Strongly preserved formulas in toposes

### Giacomo Tendas – 25 July 2018

Each (first or higher-order) language, as well as each formula on that language, can be interpreted in a topos; thus one can define the truth value of a formula and talk about Model Theory in a given topos. This talk is meant to be an overview on the higher-order formulas that are known to be "preserved" by geometric morphisms between toposes, and on Classifying Toposes for certain "preserved theories"

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