Introduction to Quantum Field Theory - 4.0

Today we will begin the last category of physics namely quantum field theory. One might ask why we need it? Isn't quantum mechanics enough? The answer is that regular quantum mechanics is not compatible with Einsteins theory of special relativity. This simply means that if we want to describe how small quantum objects move at velocities at ot near the speed of light, then we can't use regular quantum mechanics. As mentioned in the video about the hydrogen atom, we need quantum field theory to get the most accurate model of atoms. More importantly we need the framework of quantum field theory to discuss the standard model and the 3 fundamental forces, namely the strong, weak and electromagnetic force. This video is therefore to help introduce some core concepts of quantum field theory.

[srijanraman]

Ooh it'll be very helpful for us
Keep it

[PeanutButter]

Lets I dont think ill be up then but im still hyped. How long will it last?

[adityaprasad]

Thanks for this. At 8:14 you say "Thus only the commutation relation between a creation and annihilation operator is nonzero." Shouldn't that statement be "only the commutation relation between a creation and annihilation operator _with different subscripts_ is zero"? Also, what do the different subscripts represent? a_1-hat and a_2-hat are creation operators of what, exactly?

[jarikosonen]

I was interested to "see" what is happening there when there is static electric field (like between capacitor plates). How this electric field is assembled from the photonfield excitations.
What kind of photons (in terms of E=hf) there is moving between the plates to make the electric field there?

[jacobvandijk]

@ 4:06 "The mass of the field"?

[felipemarques]

Quantum Field Theory is just a formalism, a game. The world is nothing.