Math 104A (Number Theory I) - Fall 2026

Professor: CRISTIAN D. POPESCU - Lectures: TTh 9:30-10:50, in AP&M 2402.
Office Hours: TTh 8:30-9:30, AP&M 6218
Office: AP&M 6256; E-mail: cpopescu@ucsd.edu

Teaching Assistant: RAMANUJAN SRIHARI - Discussion Sections: W 5:00-5:50pm, in WLH 2114.
Office Hours: TBA.
E-mail: rsrihari@ucsd.edu

COURSE DESCRIPTION

WHAT IS MATH 104A? This is the first course in algebraic number theory for undergraduate students with background in abstract algebra. We will cover most of the material in Chapters 1 - 8 of the textbook.

TEXT Kenneth Ireland and Michael Rosen, A Classical Introduction to Number Theory, Second Edition, Springer 1990. The strongly enforced background requirement for this class is Math 100A+B or Math 103 A+B. You are strongly advised to review as soon as possible the theory of rings and fields covered in those classes, focusing on the arithmetic properties of rings (UFD, PID, ED properties.)

EXAMS

Midterm 1 - Thursday, October 22, 9:30-10:50, in AP&M 2402. Topics: TBA.
Midterm 2 - Thursday, November 19, 9:30-10:50, in AP&M 2402. Topics: TBA
Final Exam - Thursday, December 10, 8:00-11:00, in AP&M 2402. Topics: Comprehensive.
No notes, textbooks, calculators, or AI tools are allowed during exams. No make-up exams will be given and no late homework will be accepted. Cheating on an exam results in 0 points for that exam, as well as further disciplinary action.
Please read very carefully the following: ACADEMIC INTEGRITY GUIDELINES and USE OF ARTIFICIAL INTELLIGENCE POLICY.

GRADING POLICY

Midterms: 20% each; Comprehensive Final Exam: 40%; Homework (collected weekly): 20%. The grading will be done on a curve, the median corresponding to a B-/C+.

CLASSROOM CONDUCT EXPECTATIONS

Lecture attendance is mandatory. Office hour attendance is strongly encouraged.

Electronic devices: Please do not use devices (such as cell phones, laptops, tablets, iPods) for non-class-related matters while in class/section. No visual or audio recording is allowed in class/section without prior permission of the instructor (whether by camera, cell phone, or other means).

Conversations: Please avoid having private conversations with your classmates during lecture and office hours.

E-mail etiquette: I will not discuss mathematics (e.g. solutions or hints of solutions to HW problems) via email. Office hours and lectures are the best venue for that purpose. However, if you have any type of administrative questions regarding this class, please do not hesitate to send me short and to the point email messages.

IMPORTANT: The weekly HW assignments, lecture topics and exam topics will be announced in CANVAS in a timely manner.

GETTING HELP

Help with mathematical problems:

Section: Ask questions in section --- this is one of the main reasons why sections exist.
Office Hours: You are strongly advised to take full advantage of your professor's and ta's office hours.
Classmates: Sometimes a classmate can help. Sometimes you can learn by working out problems together with your classmates.

Help with personal problems which affect your class work:

Talk to the professor or, if appropriate, your college provost.