Complex analysis
Math 520, USC Fall 2025

Instructors.

Teaching assistants.

Time and location.

11am - 11:50am on Mondays, Wednesdays, and Fridays in 414 Kaprielian Hall (KAP). Note: the first class will exceptionally meet in KAP 265.

Office hours.

About.

This course is an introduction to graduate level complex analysis. The main objects of study are functions of one complex variable which are holomorphic, i.e. complex differentiable. At first glance one might expect the whole theory to closely resemble ordinary calculus of a single real variable, but in fact holomorphic functions have many remarkable features not present in the real case. In the first part of the course we will develop many fundamental ideas in complex analysis, such as holomorphic and meromorphic functions, Cauchy's theorem, integration via residues, entire functions, the Fourier transform, the gamma and zeta functions, and so on. We will then move on to more advanced topics such as the prime number theorem, conformal mappings, elliptic functions, Riemann surfaces, and more. The topics we get to in the latter part of the course will depend partly on the pace and interests of the audience.

Prerequisites.

We will assume familiarity with real analysis. Some knowledge of topology will also be helpful.

Topics.

Fundamentals: Possible advanced topics:

Textbooks and references.

Problem sets.

There will be weekly problem sets. These will be listed on this website (see the schedule below) and will be handed in via Gradescope. Late homeworks will not be accepted without prior approval from the instructor.

Much of the course material will be developed in the problem sets. It is very important to do all of the problem sets to the best of your ability and to challenge yourself to solve the problems on your own, as this is the most effective way to absorb the material. We expect students to devote a significant amount of time to the problem sets.

While working on the problem sets, you are allowed to collaborate with your peers and to consult textbooks or other references. However, you must write down attributions for any peer, textbook, website etc from which you took any significant ideas. Moreover, you must attempt all problems on your own and your submitted solutions must be written out originally and individually. Submissions which are copied or suspiciously similar are subject to being rejected and potential disciplinary action.

Final presentations.

In lieu of a midterm, we have opted to have final student presentations. More details on the structure and potential topics will be given after spring break.

Grading scheme.

TBA

Tentative schedule

Note: this schedule (along with the above information) is tentative and will be continuously updated to adapt to the pace of the course. Please check back regularly for updates and problem set assignments.
$\#$ Date Material References Problem set
1 Monday 1/13/25 Basics algebraic and topology properties of the complex numbers. Definition of holomorphic functions. [SS] Chapter 1 §1,§2
2 Wednesday 1/15/25 The Cauchy-Riemann equations and holomorphicity. Relationship with real differentiability. [SS] Chapter 1 §2.2 Pset 1 (due Thurs 1/23/25 at 11:59pm)
3 Friday 1/17/25 Recap on Cauchy-Riemann equations in terms of complex linearity of the Jacobian. Proof that the Cauchy-Riemann equations imply holomorphicity. Power series and their radii of convergence. Hadamard's formula. [SS] Chapter 1 §2.2, §2.3
Monday 1/20/25: MLK day - no class
4 Wednesday 1/22/25 Holomorphicity of power series. Piecewise smooth curves. Integrals along curves and their basic properties. Primitives. [SS] Chapter 1 §2.3, §3 Pset 2 (due Friday 1/31/25 at 11:59pm)
5 Friday 1/24/25 Statement of Cauchy's theorem, and proof in the continuously differentiable case. Proof of Goursat's theorem. [SS] Chapter 2 §1.
6 Monday 1/27/25 Cauchy's theorem in a disc and its consequences, and generalizations to "toy contours". First example of a definite integral computation using contour integration. [SS] Chapter 2 §2,§3.
7 Wednesday 1/29/25 More examples of definite integrals by contour integration. The standard Gaussian integral. Cauchy's integral formula and its proof. [SS] Chapter 2 §3,§4.
8 Friday 1/31/25 More on Cauchy's integral formula and its extension to higher derivatives. Holomorphic functions are infinitely differentiable (in particular Green's theorem holds). Cauchy's derivative bounds. Liouville's theorem and the fundamental theorem of algebra. [SS] Chapter 2 §4. Pset 3 (due Weds 2/12/25 at 11:59pm)
9 Monday 2/3/25 Proof that holomorphic functions have convergent power series. Implications for radii of convergence. Vanishing on an open set implies vanishing everywhere. Analytic continuation. Morera's theorem. [SS] Chapter 2 §4,§5.1.
10 Wednesday 2/5/25 A uniform limit of holomorphic functions is holomorphic. Holomorphic functions defined by integrating out a parameter. The symmetry principle and Schwarz reflection principle. [SS] Chapter 2 §5.2, §5.3, §5.4.
11 Friday 2/7/25 Approximating holomorphic functions on compact sets by polynomial and rational functions. Pole and zero orders of holomorphic functions. Informal statement of the residue formula. [SS] Chapter 2 §5.5, Chapter 3 §1,§2.
12 Monday 2/10/25: asynchronous class More on the singularity trichotomy. Proof of the residue formula. Examples of computing real definite integrals using the residue formula. The removable singularity theorem. [SS] Chapter 3 §1,§2.
13 Wednesday 2/12/25 Recap from last time. Characterization of poles in terms of $|f(z)|$. Statement and proof of the Casorati-Weierstrass theorem on essential singularities. Statement of the great Picard theorem. Meromorphic functions. The extended complex plane. [SS] Chapter 3 §1,§2,§3. Pset 4 (due Fri 2/21/25 at 11:59pm)
14 Friday 2/14/25 Stereographic projection and the Riemann sphere. Meromorphic functions on the extended complex plane are rational functions. The argument principle. [SS] Chapter 3 §3,§4.
Monday 2/17/25: President's Day: no class
15 Wednesday 2/19/25 Review of the argument principle. Rouché's theorem, the open mapping theorem, and the maximum modulus principle. Simply connected domains and simply connected version of Cauchy's theorem. [SS] Chapter 3 §4,§5.
16 Friday 2/21/25
17 Monday 2/24/25
18 Wednesday 2/26/25
19 Friday 2/28/25
20 Monday 3/3/25
21 Wednesday 3/5/25
22 Friday 3/7/25
23 Monday 3/10/25
24 Wednesday 3/12/25
25 Friday 3/14/25
Monday 3/17/25: spring break - no class
Wednesday 3/19/25: spring break - no class
Friday 3/21/25: spring break - no class
26 Monday 3/24/25
27 Wednesday 3/26/25
28 Friday 3/28/25
29 Monday 3/31/25
30 Wednesday 4/2/25
31 Friday 4/4/25
32 Monday 4/7/25
33 Wednesday 4/9/25
34 Friday 4/11/25
35 Monday 4/14/25
36 Wednesday 4/16/25
37 Friday 4/18/25
38 Monday 4/21/25
39 Wednesday 4/23/25
40 Friday 4/25/25
41 Monday 4/28/25
42 Wednesday 4/30/25
43 Friday 5/2/25
 
Image sources: here.