ELI5: Explain Like I'm 5

Newton–Okounkov body

Have you ever played with blocks? Imagine you have a big pile of different shaped blocks, and you want to make them fit together in a certain way to build a castle. Now imagine you want to know how the castle looks from far away, but you don't want to keep going back and forth to look at it. A Newton-Okounkov body is like taking a picture of the castle from really far away, so you can see an overall shape of it without having to look at each individual block.

Now let's talk about how we take this picture. People use something called algebraic geometry to study shapes and spaces that are described by equations. We can think of a castle, or any shape we build with blocks, as a space. When we study these shapes with algebraic geometry, we often use numbers called polynomials to describe the equations that create the spaces. The polynomials have shapes of their own, just like a building made of blocks has a shape.

The Newton-Okounkov body is a way of studying the shape of a polynomial by looking at the way it behaves when we evaluate it at different points. Evaluating means figuring out what the value of the polynomial is when we plug in different numbers. For example, if we have a polynomial that represents the amount of money we can make selling lemonade, evaluating it for different days will give us different values, because we'll sell a different amount of lemonade each day.

When we evaluate the polynomial in different ways, we get a collection of points. We can think of these points as little specks of light. Now, imagine you have a camera that can see these points very far away. You take a picture of all the points and look at the shapes they form. That final shape is the Newton-Okounkov body!

The Newton-Okounkov body can tell us a lot about the polynomial that we used to create our space, just like looking at a picture of a castle can tell us about how it was built. By studying the shape of the Newton-Okounkov body, mathematicians can learn more about the properties of the polynomial, like how many solutions it has or how it changes when we tweak its variables.