Algebraic geometry in mixed characteristic

In algebraic geometry, we study the geometry of algebraic varieties, which are sets defined by algebraic equations.
There are two types of algebraic varieties, they are varieties over characteristic zero and varieties over positive characteristic.
Algebraic geometry in characteristic zero is similar to analytic geometry, so it is related to many other subjects.
In this talk, I will introduce the notion of algebraic geometry in positive characteristic and relationships between positive characteristic and characteristic zero.
In order to study it, we consider families consisting of varieties over characteristic zero and varieties over positive characteristic, called mixed characteristic.