Extender (set theory)

In set theory, particularly in the context of large cardinals, an **extender** is a type of structure used to define certain kinds of elementary embeddings. Extenders play a crucial role in the study of large cardinal properties and help in constructing models of set theory, especially in the context of the **inner model theory**. An extender is a specific kind of object that can be used to generate ultrapowers. It is characterized by its ability to extend a certain level of consistency within set theory.