In the past, Harvard University's Department of Mathematics had described Math 55 as "probably the most difficult undergraduate math class in the country." More recently, the Math 55 lecturer in the year 2022, Professor Denis Auroux, said of the modern version, "if you’re reasonably good at math, you love it, and you have lots of time to devote to it, then Math 55 is completely fine for you."
Formerly, students would begin the year in Math 25 (which was created in 1983 as a lower-level Math 55) and, after three weeks of point-set topology and special topics (for instance, in 1994, p-adic analysis was taught by Wilfried Schmid), students would take a quiz. As of 2012, students may choose to enroll in either Math 25 or Math 55 but are advised to "shop" both courses and have five weeks to decide on one.
Depending on the professor teaching the class, the diagnostic exam may still be given after three weeks to help students with their decision. In 1994, 89 students took the diagnostic exam: students scoring more than 50% on the quiz could enroll in Schmid's Math 55 (15 students), students scoring between 10 and 50% could enroll in Benedict Gross's Math 25: Theoretical Linear Algebra and Real Analysis (55 students), and students scoring less than 10% were advised to enroll in a course such as Math 21: Multivariable Calculus (19 students).
Numbers of students dropping are due in part to the tendency of undergraduates to "shop around" for appropriate courses at the start of each semester. Even those who passed Advanced Placement Calculus and were veterans of the USA Mathematical Olympiad might feel that Math 55 was too much to handle.
In short, Math 55 gives a survey of the entire undergraduate curriculum of mathematics in just two semesters and might even include graduate-level topics. Through 2006, the instructor had broad latitude in choosing the content of the course. Though Math 55 bore the official title "Honors Advanced Calculus and Linear Algebra," advanced topics in complex analysis, point-set topology, group theory, and differential geometry could be covered in depth at the discretion of the instructor, in addition to single and multivariable real analysis as well as abstract linear algebra. In 1970, for example, students studied the differential geometry of Banach manifolds in the second semester of Math 55. In contrast, Math 25 was more narrowly focused, usually covering real analysis, together with the relevant theory of metric spaces and (multi)linear maps. These topics typically culminated in the proof of the generalized Stokes theorem, though, time permitting, other relevant topics (e.g. category theory, de Rham cohomology) might also be covered. Although both courses presented calculus from a rigorous point of view and emphasized theory and proof writing, Math 55 was generally faster paced, more abstract, and demanded a higher level of mathematical sophistication.
From 2007 onwards, the scope of the course (along with that of Math 25) was changed to more strictly cover the contents of four semester-long courses in two semesters: Math 25a (linear algebra and real analysis) and Math 122 (group theory and vector spaces) in Math 55a; and Math 25b (real analysis) and Math 113 (complex analysis) in Math 55b. The name was also changed to "Honors Abstract Algebra" (Math 55a) and "Honors Real and Complex Analysis" (Math 55b). Fluency in formulating and writing mathematical proofs is listed as a course prerequisite for Math 55, while such experience is considered "helpful" but not required for Math 25. In practice, students of Math 55 have usually had extensive experience in proof writing and abstract mathematics, with many being the past winners of prestigious national or international mathematical Olympiads (such as USAMO or IMO) or attendees of research programs (such as RSI). Typical students of Math 25 have also had previous exposure to proof writing through mathematical contests or university-level mathematics courses.
Many students who complete the course become professors in quantitative fields. Among those who took Math 55 were UC San Diego mathematician and former Harvard Dean Benedict Gross, Harvard mathematician Joe Harris, Columbia mathematical physicist Peter Woit, Harvard physicist Lisa Randall, Oxford geophysicist Raymond Pierrehumbert, Harvard economists Andrei Shleifer and Eric Maskin, and UC Berkeley economist Brad DeLong. Other alumni of Math 55 include business magnate and computer programmer Bill Gates, computer programmer and free-software promoter Richard Stallman, and television writer and executive producer Al Jean.
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Yefremova, Anastasia (May 5, 2022). "Demystifying Math 55". Department of Mathematics, Harvard University. Archived from the original on August 8, 2022. Retrieved August 25, 2022. https://web.archive.org/web/20220808194309/https://www.math.harvard.edu/demystifying-math-55/
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Compare Elkies course page (2005) and McMullen course page (2008).
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Auroux, Denis. "Math 55A Course Syllabus (Fall 2020)". Retrieved August 3, 2020. https://canvas.harvard.edu/courses/75936/assignments/syllabus
Auroux, Denis. "Math 55B Course Syllabus (Spring 2021)". Retrieved March 2, 2020. https://canvas.harvard.edu/courses/79090/assignments/syllabus
Rudin, Walter; Halmos, Paul R.; Spivak, Michael; Coates, Tom (eds.). "Honors Multivariable Calculus and Linear Algebra, Spring 2005, texts, homework, course outline". Retrieved December 9, 2018. https://archive.org/details/MATH25abHonorsMultivariableCalculusAndLinearAlgebraHarvard20042005TextsRudinHalmosSpivak/page/n9
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Williams, Sam (2002). Free as in Freedom: Richard Stallman's Crusade for Free Software. O'Reilly. p. 41. ISBN 0-596-00287-4. 0-596-00287-4
Yefremova, Anastasia (May 5, 2022). "Demystifying Math 55". Department of Mathematics, Harvard University. Archived from the original on August 8, 2022. Retrieved August 25, 2022. https://web.archive.org/web/20220808194309/https://www.math.harvard.edu/demystifying-math-55/
Yefremova, Anastasia (May 5, 2022). "Demystifying Math 55". Department of Mathematics, Harvard University. Archived from the original on August 8, 2022. Retrieved August 25, 2022. https://web.archive.org/web/20220808194309/https://www.math.harvard.edu/demystifying-math-55/
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Ury, Logan R. (December 6, 2006). "Burden of Proof". Harvard Crimson. Archived from the original on December 7, 2007. Retrieved January 17, 2023. /wiki/Logan_Ury
Bhayani, Paras D. (June 4, 2007). "Andrei Shleifer and J. Bradford DeLong". The Harvard Crimson. Retrieved December 9, 2018. "Math 55 permanently disabused me of the idea of becoming a mathematician," Shleifer says. Though he would tough the class out and remain a math major, he says he became drawn to economics—a subject he knew nothing of in high school—after taking some introductory courses in the field.. https://www.thecrimson.com/article/2007/6/4/andrei-shleifer-and-j-bradford-delong/
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@AlJean (28 January 2019). ".@TheSimpsons I actually took this class" (Tweet) – via Twitter. https://x.com/AlJean/status/1090017465751367680
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Ury, Logan R. (December 6, 2006). "Burden of Proof". Harvard Crimson. Archived from the original on December 7, 2007. Retrieved January 17, 2023. /wiki/Logan_Ury
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Elkies, Noam D. "Lecture notes for Math 55a: Honors Advanced Calculus and Linear Algebra (Fall 2002)". Retrieved December 9, 2018. http://www.math.harvard.edu/~elkies/M55a.02/index.html
Elkies, Noam D. "Lecture notes, etc., for Math 55b: Honors Advanced Calculus and Linear Algebra (Spring 200[2-]3)". Retrieved December 9, 2018. http://www.math.harvard.edu/~elkies/M55b.02/index.html
Elkies, Noam D. "Lecture notes for Math 55a: Honors Advanced Calculus and Linear Algebra (Fall 2005)". Retrieved December 9, 2018. http://www.math.harvard.edu/~elkies/M55a.05/index.html
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McMullen, Curtis T. "Math 55b: Honors Real and Complex Analysis". Retrieved December 9, 2018. http://www.math.harvard.edu/~ctm/home/text/class/harvard/55b/09/html/index.html
Elkies, Noam D. "Lecture notes for Math 55a: Honors Abstract Algebra (Fall 2010)". Retrieved December 9, 2018. http://www.math.harvard.edu/~elkies/M55a.10/index.html
Elkies, Noam D. "Lecture notes, etc., for Math 55b: Honors Real and Complex Analysis (Spring [2010-]2011)". Retrieved December 9, 2018. http://www.math.harvard.edu/~elkies/M55b.10/index.html
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Elkies, Noam D. "Lecture notes, etc., for Math 55b: Honors Real and Complex Analysis (Spring [2016-]2017)". Retrieved 2022-02-21. https://people.math.harvard.edu/~elkies/M55b.16/index.html
Auroux, Denis. "Math 55A Course Syllabus (Fall 2020)". Retrieved August 3, 2020. https://canvas.harvard.edu/courses/75936/assignments/syllabus
Auroux, Denis. "Math 55B Course Syllabus (Spring 2021)". Retrieved March 2, 2020. https://canvas.harvard.edu/courses/79090/assignments/syllabus