Phys 232A: Quantum Field Theory I
shortcut to the homework assignments
Time: Lectures: Tue and Thu, 9:40-11:00am.
Discussion sessions: Thu and Fri, 11:00am-12 noon.
Place: 402 Le Conte Hall.
Office: 401 Le Conte Hall.
GSI: Sean Jason Weinberg
Quantum field theory (QFT) and, more generally, many-body theory, represents
the leading paradigm in modern theoretical physics, and an absolutely
essential ingredient in our current understanding of the Universe on
an astonishingly diverse range of scales. The basic ideas and techniques
of QFT are at the core of our understanding of high-energy particle physics
and cosmology, as well as phenomena in condensed matter, statistical
mechanics, and even finance. QFT also naturally leads to its logical
extension -- string theory -- which in turn provides a unified framework for
reconciling the quantum paradigm with the other leading paradigm of the 20th
century physics: that of general relativity, in wich gravity is understood as
the geometry of spacetime.
At the core of the modern understanding of QFT is the so-called Wilsonian
framework: A way of understanding how interacting systems with many degrees
of freedom reorganize themselves as we change the scale at which we observe
the system. This makes concepts and techniques of QFT remarkably universal,
and applicable to just about every area of physics. As a result, a solid
understanding of the basic structure, ideas and techniques of QFT is
indispensable not only to high-energy particle theorists and experimentalists,
or condensed matter theorists, but also to string theorists, astrophysicists
and cosmologists, as well as an increasing number of mathematicians.
This course will provide the introduction to the principles of QFT, mostly in
-- but not limited to -- the special case of the relativistic regime. The
focus will be two-fold: First, on developing a "big-picture" understanding
of the basic ideas and concepts of QFT, and equally on developing the
techniques of QFT, including renormalization and the renormalization group.
The two main textbooks are going to be:
M.E. Peskin and D.V. Schroeder, An Introduction to Quantum
Field Theory (Perseus, 1995);
M.D. Schwartz, Quantum Field Theory and the Standard Model (Cambridge, 2014);
I also strongly recommend
A. Zee, Quantum Field Theory in a Nutshell. 2nd edition (Princeton U.P., 2010).
There are now many many more texts on QFT, some excellent, some not so much.
We will try to focus on the first two listed above, while adding some
additional material of interest at least occasionally, from Zee and other
sources. (In the case of Tony Zee's book, it is definitely worth buying the
2nd edition. It is substantially expanded compared to the 1st; and, notably,
many many typos of the 1st edition have also been corrected in the 2nd.)
The rough plan for what will be covered in this semester: [Peskin & Schroeder]
(or [PS] for short) consists of Parts I, II and III. We will NOT cover
anything from Part III (which deals mostly with Yang-Mills and the Standard
Model), but will cover Part I, and a big portion of Part II.
Graduate-level quantum mechanics. Basics of special relativity.
Homeworks and Grading Policy
There will be weekly homework assignments, posted on this website on Tuesdays
around noon. The homeworks will be then due in one week, on Tuesday in
The final grade will then be based on three things: 1. homeworks, 2.
participation in discussions (during discussion sessions as well as lectures),
and 3. the final exam. As I have done with other classes in previous years,
I will again apply the "two-out-of-three" rule, which was explained clearly
in class. Briefly, it means that for a good grade (say an A) it is sufficient
to do really well on two out of 1., 2. and 3. listed above; for example,
if you do great on homeworks and you interact well in discussion sessions and
lectures, you will be exempt from the final exam. (Other permutations work
HW1 (due on Tue, Sept. 16):
Problems I.2.1 and I.2.2 from [Zee]. These problems are on page 16 of the
2nd edition of the book. WARNING: In the rest of the semester, I will always
refer to the page numbers of the 2nd edition of [Zee], always ignoring the
HW2 (due on Tue, Sept. 23):
Problems 2.2.1(a,b) and 2.2.2(a) on pages 33-34 of Peskin-Schroeder ([PS] for
short), plus one problem contained in
this pdf file.
HW3 (due on Tue, Sept. 30):
Problems I.3.1 (on p. 24) and I.4.1 (p. 31) from [Zee], and Problems
2.2.2(b,c,d) on p. 34 of [PS].
HW4 (due on Tue, Oct. 7):
Problems 3.1(a) (on p. 71) from [PS], I.3.3 (p. 24) and I.5.1 (p. 39)
HW5 (due on Tue, Oct. 14):
Problems 3.1(b,c), 3.2, 3.4(a,b,c) (on pp. 72-74) from [PS].
HW6 (due on Tue, Oct. 21):
Problem 3.5 (on pp. 74-5) from [PS], Problem I.7.2 from [Zee, p. 60],
Problem 4.3(a) from [PS, p.127-8]; please do only the first part of this
problem (a), including the propagator and the vertex but excluding the
HW7 (due on Tue, Oct. 28):
Problems 4.1(a,b,c) and 4.3(b,c) from [PS] (on pages 126-129). Apologies for
the slight delay in the posting of this assignment.
HW8 (due on Tue, Nov. 4):
Problem 4.4(a,b,c) from [PS] (on pages 129-30), and the part of 4.3(a) which
deals with the differential cross-section and was left out in HW6.
HW9 (due IN NINE DAYS, on Thu, Nov. 13 -- no class on Tue, Nov 11: Veterans' Day):
Problems 5.1 and 5.2 from [PS, pp.169-70], Problem III.1.3 from [Zee, p. 168],
and Problem VI.8.2 (only the case of the lambda phi^4 theory) from
[Zee, p. 368].
HW10 (due on Thu, Nov. 20): Problems III.2.1
[Zee, p. 172], III.3.1, III.3.2, III.3.4 and III.3.5 [Zee, p. 181].
HW11 (due on Tue, Dec. 2): Problems IV.3.3, IV.3.4 and
IV.3.5 (on page 244 of [Zee]), Problem 6.3(a) (on page 210 of [PS]).