## Beginnings

August 29, 2013

Tuesday, August 27, 2013. First day of school.

(Friday night. “What do you mean I begin classes on Monday?”)

## 414/514 – Advanced calculus aka Analysis I – Syllabus

August 25, 2013

Instructor: Andrés E. Caicedo.
Contact Information: See here.
Time: MWF 10:30-11:45 am.
Place: Mathematics building, Room 124.
Office Hours: Th 1:30-3:00 pm. (Or by appointment.)
Text:

1. Pugh, Charles Chapman. Real mathematical analysis. Springer, 2002.
2. Spivak, Michael. Calculus On Manifolds: A Modern Approach To Classical Theorems Of Advanced Calculus. Westview Press, 1971.

Contents: Math 414/514 is an introduction to Analysis on Euclidean spaces (${\mathbb R}^n$). The emphasis is theoretical, as opposed to the more computational approach of calculus. From the Course Description on the Department’s site:

Introduction to fundamental elements of analysis on Euclidean spaces including the basic differential and integral calculus. Topics include: infinite series, sequences and series of function, uniform convergences, theory of integration, implicit function theorem and applications.

Grading: Based on homework. No late homework is allowed. Collaboration is encouraged, although you must turn in your own version of the solutions, and give credit to books/websites/… you consulted and people you talked/emailed/… to.

I do not want to have exams in this course. However, an important component of being proficient in mathematics is a certain amount of mental agility in recalling notions and basic arguments. I plan to assess these by requesting oral presentations of solutions to some of the homework problems throughout the term. If I find you lacking here, it will be necessary to have an exam or two. The final exam is currently scheduled for Wednesday, December 18, 2013, 12:00 – 2:00 pm.

On occasion, I post links to supplementary material on Google+. Circle me and let me know if you are interested, and I’ll add you to my Analysis circle. As with this blog, I encourage you to comment there.

## 170 – Calculus I (Honors). Syllabus

August 25, 2013

Math 170 Section 8: Calculus I. Honors.

Instructor: Andres Caicedo.

Contact Information: See here.
Time: MWF 1:30-2:45 pm.
Place: Mathematics building, Room 139.
Office Hours: (I expect they will be on) Th 1:30-3:00 pm, or by appointment (email me a few times/dates you have available).

Text:

2. We will complement with exercises from Schaum’s Outlines Calculus, Frank Ayres Jr and Elliot Mendelson, Sixth Edition, McGraw Hill, 2012.
3. There will be additional material, in the form of extracts from other books, articles from mathematical magazines, discussions online, and some group exercises from Applications of Calculus, Philip Straffin, ed., Resources for Calculus Collection, Vol. 3, MAA notes, Vol. 29, 1993; these will be provided as needed.

Please make sure each day you bring to class a copy of the pages that are being covered from the online text, according to the list below; this may be an electronic copy. (To be safe, bring at least the pages corresponding to the sections for that day, for the previous day, and for the next day, since I may cover a bit more than what is scheduled, and we may need to refer back to recently covered material.)

Contents: The department’s course description reads:

Definitions of limit, derivative and integral. Computation of the derivative, including logarithmic, exponential and trigonometric functions. Applications of the derivative, approximations, optimization, mean value theorem. Fundamental Theorem of Calculus, brief introduction to applications of the integral and to computations of antiderivatives.

Our emphasis is on understanding the theory, but we will also cover some applications. Roughly, I expect we will see Sections 1.1-8.1, 9.1-9.2. This list includes somewhat more than strictly required, giving us a little additional time in case we want or need to emphasize some topics. Please bookmark this post. I update it frequently with detailed week-to-week descriptions.

Detailed day to day description and homework assignments. All problems are from the Whitman calculus book unless otherwise explicitly specified:

• August 26. Sections 1.1, 1.2. Homework: 1.1: 3, 6, 9, 12. 1.2: 1(d,e,f), 2(d,e,f), 5.
• August 28. Sections 1.2, 1.3. Homework: 1.3: 4, 9, 14, 16.
• August 30. Sections 1.3, 1.4. Homework: 1.4: 7, 11, 17, 19. Quiz 1, on sections 1.1-1.3.

The first homework set is due Wednesday, September 4. It consists of all the problems listed above. See below for the required format.

• September 4. Sections 2.1, 2.2. Homework 1 is due today. Homework: 2.1: 1, 3, 4, 7. [The following problems from the Schaum’s book are strongly suggested, but not required: Chapter 1 (Supplementary problems): 10-16; Ch. 9 (Solved problems): 1-10; (Supplementary problems): 14-17.]
• September 6. Sections 2.2, 2.3. Homework: 2.2: 2, 3. 2.3: Homework: 2, 5, 11-15, 17, 18. [The following problems from the Schaum’s book are strongly suggested, but not required: Ch. 7 (Solved): 9-12; (Suppl.): 16, 17, 22, 23.] Quiz 2.

The second homework set is due Monday, September 9. It consists of all the problems from the Whitman book listed on September 4 and 6. See below for the required format.

• September 9. Section 2.3 (continued). Homework 2 is due today.
• September 11. Section 2.4. Homework: 2, 4, 7 [Suggested problems from Schaum’s: Ch. 9 (Solved): 11; (Suppl.): 18, 19, 22-24.]
• September 13. Section 2.5. Quiz 3, on Sections 2.3, 2.4. Homework: 3, 5, 7 [Suggested problems from Schaum’s: Ch. 8 (Solved): 2; (Suppl.): 4-8.]

The third homework set is due Monday, September 16. It consists of all the problems from the Whitman book listed on September 11 and 13. See below for the required format.

• September 16. Sections 3.1-3.3. Errol Morris‘s essay on Hypassus of Metapontum. Homework 3 is due today. Homework: 3.1: 3, 4, 6. 3.2: 3-5, 8, 10. 3.3: 2, 4, 5. [Suggested problems from Schaum’s: Ch. 10 (Solved): 1, 2(4,6), 5-9; (Suppl.): 27-33, 43.]
• September 18. Sections 3.4, 3.5. Homework: 3.4: 2, 4, 6, 9. [Suggested problems from Schaum’s: Ch. 10 (Solved): 2(7); (Suppl.): 35, 44.]
• September 20. Group activity 1. Due Wednesday, September 25. Arbitrating disputes, by Philip Straffin, pp. 7-21 of Applications of Calculus. Extra credit project posted, due December 2.

The fourth homework set is due Monday, September 23. It consists of all problems from the Whitman book listed on September 16 and 18. See below for the required format.

• September 23. Homework 4 is due today. Sections 4.1-4.3, and Schaum’s chapter 16. Review of basic trigonometric identities. Homework: Section 4.1: 3, 9, 11. [Suggested problems from Schaum’s: Ch. 16 (Solved): 1-7, 11-12; (Suppl.): 1-22. Ch. 17 (Solved): 1; (Suppl.): 21-24, 26.]
• September 25. Group activity 1 is due today. Sections 4.3-4.5. Homework: Section 4.3: 3, 5, 6. Section 4.4: 2, 3, 4.
• September 27. Midterm 1. It covers the material from the first 3 chapters of the book, with emphasis on Chapters 2 and 3.

The fifth homework set is due Monday, September 30. It consists of all problems from the Whitman book listed on September 23 and 25. See below for the required format.

The sixth homework set is due Monday, October 7. It consists of all problems from the Whitman book listed on September 30 and October 2. See below for the required format.

• October 7. Sections 4.8, 4.9. Celestial mechanics and Kepler’s equation. Kepler’s laws of planetary motion state that the orbits of celestial bodies are ellipses; the prevailing theory was that orbits were perfect circles, this was based on the old theory of epicycles that goes back to Ptolemy, when it was still believed that the Earth was the center of the universe. Here is an illustration of how useless as an explanatory theory this is. Homework: Section 4.7: 2, 6, 10, 12, 16. Section 4.8: 2, 5, 6, 11, 14. [Suggested problems from Schaum’s: Ch. 25 (Suppl.): 8, 10, 11, 12, 15; Ch. 26 (Solved): 1, 2, 4, 6, 7; (Suppl.): 8, 11, 17-20.]
• October 9. Sections 4.9, 4.10. L’Hôpital controversy (see also here). Homework: Section 4.9: 2, 5, 6. Section 4.10: 2, 5, 7, 14, 20. [Suggested problems from Schaum’s: Ch. 7 (Solved): 3, 7 (Suppl.): 17, 18; Ch. 27 (Solved): 1-4; (Suppl.): 7, 10.]
• October 11. Quiz 5. Sections 4.10, 4.11. Hyperbolic functions.

The seventh homework set is due Monday, October 14. It consists of all problems from the Whitman book listed on October 7 and 9. See below for the required format.

• October 14. Sections 5.1, 5.2. Homework: Section 5.1: 4, 6, 8, 10, 16. Section 5.2: 4, 6, 8, 10, 14. [Suggested problems from Schaum’s: Ch. 14 (Solved): 1, 4, 5, 7, 8; (Suppl.): 23, 26.]
• October 16. Sections 5.3, 5.4, 5.5. Homework: Section 5.3: 2, 4, 6, 8, 9, 12. Section 5.4: 2, 4, 6, 8. [Suggested problems from Schaum’s: Ch. 14 (Solved): 2, 3, 6, 9; (Suppl.): 24. Ch. 15 (Solved): 1-8; (Suppl.): 11, 12; Ch. 17 (Solved): 14; (Suppl.): 29.]
• October 18. Group activity 2. Due Wednesday, October 23. Somewhere within the rainbow, by Steven Janke, pp. 42-53 of Applications of Calculus.

The eight homework set is due Monday, October 21. It consists of all problems from the Whitman book listed on October 14 and 16. See below for the required format.

• October 21. Section 6.1. Richard Feynman on the Scientific method. Homework: Section 5.5: 2, 7, 10, 15, 19, 23, 30, 32. [Suggested problems from Schaum’s: Ch. 15 (Solved): 9-10; (Suppl.): 13; Ch. 17 (Solved): 15.]
• October 23. Group activity 2 is due today. Section 6.1.
• October 25. Quiz 6. Section 6.1. Homework: 6.1: 3, 5, 8, 11, 15. [Suggested problems from Schaum’s: Ch. 14 (Solved): 1, 11, 12, 14, 18; (Suppl.): 26-30.]

The ninth homework set is due Monday, October 28. It consists of all problems from the Whitman book listed on October 21 and 25. See below for the required format.

• October 28. Section 6.2. Homework: 6.2: 5, 6, 9, 15, 17, 19. [Suggested problems from Schaum’s: Ch. 20: All problems.]
• October 30. Sections 6.2, 6.3. Homework: 6.3: 2, 3.
• November 1. Midterm 2. It covers the material from the book up to and including section 6.2. Emphasis on the material from Chapter 4 on.

The tenth homework set is due Monday, November 4. It consists of all problems from the Whitman book listed on October 28 and 30. See below for the required format.

The eleventh homework set is due Monday, November 11. It consists of all problems from the Whitman book listed on November 4 and 6. See below for the required format.

• November 11. Section 7.1. Riemann sums. Homework: 7.1: 2, 4, 6, 8.
• November 13. Section 7.2. “The birth of the calculus,” produced by The Open University, and narrated by Jeremy Gray.
• November 15. Group activity 3. Due Wednesday, November 20. Speedy sorting, by Steven Janke, pp. 223-238 of Applications of Calculus. A reason why we care about “fast” counting/sorting techniques, is usually called combinatorial explosion, see here. An illustration of sorting algorithms through folk dance. A visualization of 15 sorting algorithms.

The twelfth homework set is due Monday, November 18. It consists of all problems from the Whitman book listed on November 11. See below for the required format.

• November 18. Section 7.2. Homework: 2, 4, 6, 8, 10, 12, 14, 16, 18, 20. [Suggested problems from Schaum’s: Ch. 24 (Solved): 1-5; (Suppl.): 8-26, 29, 31.]
• November 20. Group activity 3 is due today. Section 7.3. Homework: 2, 3, 5. [Suggested problems from Schaum’s: Ch. 24 (Solved): 6; (Suppl.): 27, 28, 30, 32, 37; Ch. 25 (Solved): 1; (Suppl.): 13, 14, 17.]
• November 22. Midterm 3. It covers the material from the book up to and including section 7.2. Emphasis on the material from Chapters 6 and 7.

The week of November 25-November 29 is Thanksgiving break (Happy thanksgiving!). The thirteenth homework set is due Monday, December 2. It consists of all problems from the Whitman book listed on November 18 and 20. The extra credit project is also due December 2.

• December 2. Section 8.1. Homework: Section 8.1: 2, 6, 7, 10, 16, 18. [Suggested problems from Schaum’s: Ch. 24 (Suppl.): 34; Ch. 25 (Solved): 5; (Suppl.): 9; Ch. 26 (Suppl.): 9.]
• December 4. Section 9.1. Mechanical devices to measure areas: A “tannery mechanical surface integrator“, and a Planimeter. Fermat’s method of quadratures. (Adequality.) (The link to Fermat’s method is to a write up by Fred Rickey. Other interesting short notes on his page can be found here. Translation of Fermat’s papers, including his paper on quadratures, can be found at a curious website, here.) Homework: Section 9.1: 3, 4, 8, 11.
• December 6. Quiz 8. Section 9.2. Terminal velocity, Felix Baumgartner. Supplement: Falling raindrops, by Walter J. Meyer, pp. 101-111 of Applications of Calculus.

The fourteenth homework set is due Monday, December 9. It consists of all problems from the Whitman book listed on December 2 and 4. See below for the required format.

There is no assigned homework set for this week.

Homework: There is weekly homework, due Mondays at the beginning of lecture; you are welcome to turn in your homework early, but I will not accept homework past Mondays at 1:35 pm. The homework consists on the problems assigned during the previous week. It is a good idea to work daily on the homework problems corresponding to the material covered that day. A grader (Blake Oren) will check your homework for completeness, and grade carefully 1 or 2 questions (each homework is graded out of 10 points, completeness is worth 2 points). You should use it as a guide for what material to focus on, and what kind of skills are required from you. It is a very good idea to do all of the assigned homework. During office hours, you are welcome to ask about problems from the assigned sets (or any other problems you find interesting). Frequently, some (but not necessarily all) of the problems from the quizzes will be fairly close, if not outright identical, to homework problems.

Your homework must follow the format developed by the mathematics department at Harvey Mudd College. You will find that format at this link. If you do not use this style, your homework will be graded as 0.

Quizzes: There will be weekly quizzes, on the last 20 minutes of Friday’s lecture. Each quiz will evaluate, roughly, the material covered from Friday to Wednesday. You are not allowed to only show up about 20 minutes before the end of the lecture in order to take the quiz; if you show up only for the quiz, your score is 0. If you fail to take a quiz, it will be scored as 0. There are no make-up quizzes. The lowest score is dropped.

For each quiz, I will provide you with a page with the question(s) printed. You may use this page to solve the questions. You need to bring any additional pieces of paper you may require. Calculators, notes, textbooks are allowed. Most likely I will not have calculators, or pencils, etc, so bring your own.

Exams: There will be 3 in-class exams (dates to follow) and a comprehensive final exam.

• Midterm 1: Friday, September 27.
• Midterm 2: Friday, November 1.
• Midterm 3: Friday, November 22.
• Final exam: Wednesday, December 18, 2013; 2:30 – 4:30 pm. This exam is cumulative, including material from handouts and group activities.

The grade will be decided based on homework (17% of the total score), quizzes (17%), group work (16%), the three in-class exams (10% each), and a final exam (20%).

I will then grade on a linear scale:

• If your final score is 90% or higher, you receive an A.
• If it is between 80 and 89%, you receive a B.
• If it is between 70 and 79%, you receive a C.
• If it is between 60 and 69% you receive a D.
• If it is 59% or lower, you receive an F.

Attendance: Not required, but encouraged. Any material covered in lecture may be used in quizzes and exams, even if it is not discussed in the textbooks. I will use this website to post any additional information, and encourage you to use the comments feature, but (in general) I will not post here standard content covered in the textbooks or in class. If you leave a comment, please use your full name, which will simplify my life filtering spam out.

Please pay attention to the Student Code of Conduct. Feel free to ask me if there are any questions.

I post links to supplementary material on Google+. Circle me and let me know if you are interested, and I’ll add you to my Calculus circle. As with this blog, I encourage you to comment there.

## Interpretations

August 18, 2013

(This started as an answer on Math.Stackexchange. This version has been lightly edited and expanded. Also posted at fff.)

Throughout this post, theory means first-order theory. In fact, we are concerned with theories that are recursively presented, though the abstract framework applies more generally. Thanks to Fredrik Engström Ellborg for suggesting in Google+ the reference Kaye-Wong, and to Ali Enayat for additional references and many useful conversations on this topic.

1.

Informally, to say that a theory $T$ interprets a theory $S$ means that there is a procedure for associating structures $\mathcal N$ in the language of $S$ to structures $\mathcal M$ in the language of $T$ in such a way that if $\mathcal M$ is a model of $T$, then $\mathcal N$ is a model of $S$.

Let us be a bit more precise, and do this syntactically to reduce the requirements of the metatheory. The original notion is due to Tarski, see

Alfred Tarski. Undecidable theories. In collaboration with Andrzej Mostowski and Raphael M. Robinson. Studies in Logic and the Foundations of Mathematics. North-Holland Publishing Company, Amsterdam, 1953. MR0058532 (15,384h).

I follow here the modern reference on interpretations,

Albert Visser, Categories of theories and interpretations, in Logic in Tehran, Lecture Notes in Logic, vol. 26, Association for Symbolic Logic, La Jolla, CA, 2006, pp. 284–341. MR2262326 (2007j:03083).

One can take “the theory $T$ interprets the theory $S$ to mean that there are

1. A map $i$ that assigns formulas in the language of $T$ to the symbols of the language $\mathcal L$ of $S$, and
2. A formula $\mathrm{Dom}(x)$ in the language of $T$,

with the following properties: We can extend $i$ to all $\mathcal L$-formulas recursively: $i(\phi\land\psi)=i(\phi)\land i(\psi)$, etc, and $i(\forall x\phi)=\forall x(\mathrm{Dom}(x)\to i(\phi))$. It then holds that $T$ proves

1. $\exists x\,\mathrm{Dom}(x)$, and
2. $i(\phi)$ for each axiom $\phi$ of $S$ (including the axioms of first-order logic).

Here, $T,S$ are taken to be recursive, and so is $i$.

If the above happens, then we can see $i$ as a strong witness to the fact that the consistency of $T$ implies the consistency of $S$.

Two theories are mutually interpretable iff each one interprets the other. By the above, this is a strong version of the statement that they are equiconsistent.

Two theories are bi-interpretable iff they are mutually interpretable, and in fact, the interpretations $i$ from $T$ is $S$ and $j$ from $S$ in $T$ can be taken to be “inverses” of each other, in the sense that $T$ proves that $\phi$ and $j(i(\phi))$ are equivalent for each $\phi$ in the language of $T$, and similarly for $S$, $\psi$ and $i(j(\psi))$. In a sense, two theories that are bi-interpretable are very much “the same”, only differing in their presentation.

## Hindsight

August 11, 2013

From Georg Kreisel‘s review of The decision problem for exponential diophantine equations, by Martin Davis, Hilary Putnam, and Julia Robinson, Ann. of Math. (2), 74 (3), (1961), 425–436. MR0133227 (24 #A3061).

This paper establishes that every recursively enumerable (r.e.) set can be existentially defined in terms of exponentiation. […] These results are superficially related to Hilbert’s tenth problem on (ordinary, i.e., non-exponential) Diophantine equations. The proof of the authors’ results, though very elegant, does not use recondite facts in the theory of numbers nor in the theory of r.e. sets, and so it is likely that the present result is not closely connected with Hilbert’s tenth problem. Also it is not altogether plausible that all (ordinary) Diophantine problems are uniformly reducible to those in a fixed number of variables of fixed degree, which would be the case if all r.e. sets were Diophantine.

Of course, my favorite quote in relation to the tenth problem is from the Foreword by Martin Davis to Yuri Matiyasevich’s Hilbert’s tenth problem.

During the 1960s I often had occasion to lecture on Hilbert’s Tenth Problem. At that time it was known that the unsolvability would follow from the existence of a single Diophantine equation that satisfied a condition that had been formulated by Julia Robinson. However, it seemed extraordinarily difficult to produce such an equation, and indeed, the prevailing opinion was that one was unlikely to exist. In my lectures, I would emphasize the important consequences that would follow from either a proof or a disproof of the existence of such an equation. Inevitably during the question period I would be asked for my own opinion as to how matters would turn out, and I had my reply ready: “I think that Julia Robinson’s hypothesis is true, and it will be proved by a clever young Russian.”