ELI5: Explain Like I'm 5

Common integrals in quantum field theory

Okay, kiddo, let's first understand what an integral means. You know how you add up numbers, like 2 + 2 becomes 4, right? Well, an integral is kind of like a fancy way of adding up a lot of those numbers - except instead of adding, you're figuring out the total size of some shape, like a curve or a surface.

Now, in quantum field theory, there are some shapes that we use very often to describe how particles move and interact with each other. These shapes have been studied a lot over the years, and we've figured out some very useful formulas for calculating their sizes using integrals.

One of the most common shapes we work with is called a "propagator". This is basically a fancy way of describing how a particle travels from one point in space to another. To figure out the total size of a propagator, we use what's called a "Feynman integral" - named after a really famous physicist who helped develop quantum field theory.

Another important shape in quantum field theory is a "loop". This is a type of curve that can wrap around itself multiple times (like a roller coaster doing several loops). To calculate the size of a loop, we use what's called a "vacuum bubble integral" - which, unfortunately, has nothing to do with blowing bubbles.

Finally, there are also some integrals we use to describe how particles can interact with each other in different ways. These are called "vertex integrals", and they help us figure out the probability of certain types of particle interactions happening.

So, that's the basic idea, kiddo. Integrals are a way of figuring out the size of shapes, and in quantum field theory, we use them a lot to study particles and their interactions. The three types of integrals I mentioned - Feynman, vacuum bubble, and vertex - are some of the most commonly used ones in this field.