Recommendations by friend P. C.:
Lecture notes found by Googling "quantum field theory pdf":
These seem very direct and not ultra advanced, good read.
Author: David Tong.
Number of pages circa 2021: 155.
It should also be noted that those notes are still being updated circa 2020 much after original publication. But without Git to track the LaTeX, it is hard to be sure how much. We'll get there one day, one day.
Some quotes self describing the work:
A follow up course in the University of Cambridge seems to be the "Advanced QFT course" (AQFT, Quantum field theory II) by David Skinner: www.damtp.cam.ac.uk/user/dbs26/AQFT.html
Author affiliation: University of California, Santa Barbara.
Number of pages: 616!
Don't redistribute clause, and final version by Cambridge University Press, alas, so corrections will never be merged back: web.physics.ucsb.edu/~mark/qft.html. But at least he's collecing erratas for the published (and therefore draft) versions there.
The book is top-level organized in spin 0, spin half, and spin 1. Quite ominous, really.
The preface states that one of its pedagogical philosophies is to "Illustration of the basic concepts with the simplest examples.", so maybe there is hope after all.
45 1 hour lessons. The Indian traditional music opening is the best.
10 2-hour lessons.
Lecturer: Leonard Susskind.
14 1 hours 20 minute lectures.
The video resolution is extremely low, with images glued as he moves away from what he wrote :-) The beauty of the early Internet.
This is a bit "formal hocus pocus first, action later". But withing that category, it is just barely basic enough that 2021 Ciro can understand something.
Lecture notes transcribed by a student: github.com/avstjohn/qft
18 1h30 lectures.
Bibliography review:
Course outline given:
Non-relativistic QFT is a limit of relativistic QFT, and can be used to describe for example condensed matter physics systems at very low temperature. But it is still very hard to make accurate measurements even in those experiments.
Defines "relativistic" as: "the Lagrangian is symmetric under the Poincaré group".
Mentions that "QFT is hard" because (a finite list follows???):
There are no nontrivial finite-dimensional unitary representations of the Poincaré group.
But I guess that if you fully understand what that means precisely, QTF won't be too hard for you!
Notably, this is stark contrast with rotation symmetry groups (SO(3)) which appears in space rotations present in non-relativistic quantum mechanics.
  • something about finding a unitary representation of the poincare group
Interactions.
Dirac field.
Dirac equation.
When the word "advanced" precedes QFT, you know that the brainrape is imminent!!!
Big goal: explain the Standard Model.
Gaussian path integrals.
This book really tries to recall basic things to ensure that the reader will be able to understand the more advanced ones.
Sometimes it goes a little bit overboard, like defining what a function does several times.
But Ciro Santilli really prefers it when authors error on the side of obvious.
People are mostly saying you have to be a more of a genius amateur to read it.
ISBN-13: 978-0691140346
lecture 1 mentions that this book is quick and dirty, as one might guess from the title. Ciro Santilli thinks he's gonna like this one.
First edition: from 2003, www.amazon.com/dp/0691010196, ISBN-13: 978-0691010199.
This didn't really deliver. It does start from the basics, but it is often hard to link those basics to more interesting or deeper points. Also like many other Quantum field theory book, it does not seem to contain a single comparison between a theoretical result and an experiment.
This is very widely used in courses as of 2020, it became kind of the default book.
Unfortunately, this approach bores Ciro Santilli to death. Or perhaps is too just advanced for him to appreciate. Either of those.
800+ pages.