what's the difference between QFT and Atomic physics

robertjford80

For physics between QM and String Theory I've heard a lot of different names.

Quantum Electrodynamics seems to be the physics of the electron and the photon.

Quantum Chromodynamics seems to be the physics of quarks.

But High Energy/Nuclear/Particle Physics, Atomic physics, QFT, I don't know what the difference between them is. This forum has one category for HE/N/P physics and another for atomic physics so there has to be some difference.

kurros

Atomic physics - study of atomic interactions
Nuclear physics - study of nuclear interactions
High energy/particle physics - study of fundamental particle interactions
QFT - the underlying mathematical theory of particle interactions, the particle world version of Newtons laws of motion. You take QFT and put various sorts of particles into it to create QED, QCD etc.

bapowell

Atomic physics is the application of quantum mechanics to the atom, to study, as kurros says, atomic interactions and behavior.

In order to study the interactions of light and matter (QED), we need a relativistic version of quantum mechanics -- this is quantum field theory. So QED and QCD are physical theories based on QFT.

High energy physics is basically synonymous with particle physics, which is the study of the elementary particles and forces of nature. Modern particle physics is based on the Standard Model, which encompasses QED, QCD, and the theory describing the electroweak force.

So, really you have:

Atomic physics <----- Quantum mechanics
Particle physics (high energy physics) <------- QED, QCD, others <------- QFT
Nuclear physics <------- QCD, others <------- QFT, others

nrqed

To be more precise, QFT is required to do precision atomic physics (the most obvious and historically first example is the Lamb shift calculation). Quantum mechanics as taught in undergraduate physics classes is not sufficient to do precision atomic physics (for example second order perturbation theory of most interactions gives infinite results).