Finally Taking Quantum Field Theory 1

It's been 2 years since I've taken Quantum Field Theory II and now I'm finally taking part 1. I talk about how I'm approaching the class and how its going!

[samanwayapatra]

Learning delta function is the most accurate description I have ever heard

[FreeRoger]

Andrew lives in a non-linear timeline where you have to take E&M, then Classical Mechanics, then GR, then QFT 2, then kinematics, then QFT1.

[uzulim]

I was a number theorist by training, and I took a first course to QFT, 2 years ago. Needless to say, the vacuum of rigor was quite shocking to me at the time. Now I have a better sense of how to approach the subject, partly by seeing it as a collection of calculation techniques held together by heuristics.

[GaugeMcArora]

Hey guys, I just want to share my favourite physics book which covers the topics which Andrew mentioned to be difficult to grasp. The book is 'Physics from Symmetry' by Jakob Schwichtenberg. It covers group representation in different dimensions and Lie Algebra of SO(3) and Lorentz group pretty well. My favourite of this book is the way it covers Classic field theory. He derives the dirac equation and gamma matrices for spinor fields, Klien Gordon equation for scalar fields and Proca equation for vector fields and He makes it look very simple. I highly recommend that book to all Physics Aspirants.

[spinor]

The classification of particles via unitary irreps of the Poincaré group is honestly to me one of the most mindblowing things in physics. It's amazing that we can show that quantities such as mass and spin (as well as other charges) are necessary properties of fundamental states that obey the symmetries of the universe. So elegant! That's why I like the "particle-to-field" approach Weinberg takes in his QFT Vol. 1. That book is great for getting a firm grasp on the foundations of QFT.

[tomclark]

Hi Andrew, thank you so much for inspiring me to change my degree and swap to physics. Best decision I've ever made :)

[TWI]

I’m glad I’m not the only one who spends a lot of time on trying to understand every single step in a proof

[varunv]

"but I'll spend hours thinking about why that step makes sense" literally me when it comes to A levels Physics. Glad to know I'm not alone with this habit.

[bensparrow]

That delta function joke is hella funny I LOLed at that!

[someperson]

The video quality is strangely professional

[siddharthpenmetsa]

Hey, i just wanna say thank you, you really are the one reason i got so invested in math and physics in 8th grade, I’m now planning to do a physics degree pretty much as a result of watching your videos

[エブリエルマスター]

QFT's making him more of a Chad that he was before

[farfa]

That tensor playlist is being so helpful, I stated studying physics like a month ago (all by myself) and it's a nice challenge while I'm practicing more basic calculus since I took those classes eons ago. Thanks for making it!

[brandonwalker]

Learning delta function really got me. Both a great joke and a really apt description of how it feels to get into many advances topics.

[cauliemac]

Every time I watch one of these explanation videos I'm both fascinated and horrified that there's so much complex physics out there. And I'm in my final year of undergrad

[dcTHEcook]

We did second quantization in our bachelors hahahaha one of the earliest homeworks was to prove the bogoliougov transformations. A true learning delta function

[zackarysemancik]

Learning delta function made me chuckle. That's a good one.

[samirdakal]

We had to study two different textbook for the QFT class. One used subscripted gamma another used superscripted gamma. Rules of commutation were different for different kind of gamma. I spent huge amount of time in figuring out similarities and differences between these gammas. Beside this, QFT class went really well.

[PrettyMuchPhysics]

Concerning 04:05, equation (13) in your PDF tells us that the combination \bar\psi\gamma^\mu\psi (one type of Dirac bilinear) transforms as a four-vector. If you take eq. (13) and put a \bar\psi on the left and a \psi on the right (on both sides of the equation), then you get the equivalent of x^\mu = \Lambda^\mu_\nu x^\nu. This is because \psi transforms with \Lambda_1/2 and \bar\psi with \Lambda_1/2^\dagger under a Lorentz transformation (also note that the \gamma^0 inside the \bar\psi is necessary for this to work since the \Lambda_1/2 are not unitary/the generators are not Hermitian. For more information, see the discussion above eq. (3.33) in Peskin&Schroeder). Looking forward to your next video on QFT ☺️👍

[liederivative]

Once you've finished the course, could you make a compare and contrast video between the 2nd quantization and Feynman path integral formulations of QFT? I've always felt super weird using the latter