ELI5: Explain Like I'm 5

Perron–Frobenius theorem

The Perron-Frobenius Theorem is all about what happens when we have a big matrix full of numbers. Imagine a square made up of tiny squares, each with a number inside. This is what we call a matrix.

The Perron-Frobenius Theorem tells us something cool about this matrix. Let's say that all of the numbers inside the matrix are bigger than 0. If we keep multiplying the matrix by itself over and over again, eventually we'll get some really big numbers. In fact, there will be one number that's bigger than all the others, and it'll keep getting bigger every time we multiply the matrix by itself.

This special number is called the dominant eigenvalue. It's like the king of all the numbers in the matrix. And because it's so important, there's a whole bunch of other stuff that we can figure out about the matrix based on this one number.

For example, we can figure out how fast the other numbers in the matrix grow compared to the dominant eigenvalue. We can also find out which direction the numbers grow in. This is important in lots of different areas, like computer science, physics, and economics.

So, to sum up: Perron-Frobenius Theorem tells us that when we have a big matrix full of positive numbers, there's one really important number that's bigger than all the others. And this special number helps us learn all sorts of interesting things about the matrix!