Polarization in Lie algebra refers to a way of splitting a Lie algebra into two parts. A Lie algebra is a collection of mathematical objects called matrices or vectors that can be used to do calculations in areas like mechanics or physics.
Imagine you have a bunch of building blocks, some of which are red and some of which are blue. You want to sort them into two groups so that all the red ones are in one group and all the blue ones are in the other group.
In the same way, we can separate the elements in a Lie algebra into two sets based on a property called an eigenvalue. This eigenvalue is like a label we put on each element to identify it.
So, if we have a Lie algebra that's made up of a bunch of matrices, we can separate them into two sets - one set where all the eigenvalues are positive or zero, and another set where all the eigenvalues are negative or zero.
This is useful because we can use the two sets to represent different parts of a physical system. For example, in mechanics we might use one set of matrices to represent position and another to represent momentum. Separating the matrices into the two sets lets us perform calculations that take into account both position and momentum.
Overall, polarization helps us use the Lie algebra to describe different aspects of a system by splitting it into two parts based on a simple mathematical property.