# What is coupling in QFT?

I'm an experimentalist, so go easy on me... What does it mean for a particle to either couple or not couple to a field? I haven't taken a class in QFT yet, so please try to explain the general idea without any details or equations!

e.bar.goum
As an experimentalist as well, my working understanding is that you may replace "couple" with "interact". E.g. W± couples with the electromagnetic field = W± interacts with the electromagnetic field.

BucketOfFish
atyy
In the Lagrangian, the coupling between two fields is a term in which the two fields are multiplied together. A free scalar field has only up to quadratic terms, so if one adds cubic or higher order terms, those are sometimes said to be self-interaction terms. http://www.damtp.cam.ac.uk/user/tong/qft/three.pdf gives an example of a self-interaction term (Eq 3.5), and an example of an interaction between two different types of fields (3.7)

BucketOfFish
I'm an experimentalist, so go easy on me... What does it mean for a particle to either couple or not couple to a field? I haven't taken a class in QFT yet, so please try to explain the general idea without any details or equations!

An example: particles with electric charge couple to the electromagnetic field. Electrically neutral particles do not couple to the electromagnetic field.

dextercioby