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exposition, math

Mathematical Information II

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Introduction

This is the second post about Mathematical Information inspired by talks the AMS meeting in Seattle in January, 2016. The first post was Mathematical Information I. That post covered, among other things, types of explanations.

In this post as in the previous one, footnotes link to talks at Seattle that inspired me to write about a topic. The speakers may not agree with what I say.

The internet

Math sources on the internet

Publishing math on the internet

  • Publishing on the internet is instantaneous, in the sense that once it is written (which of course may take a long time), it can be made available on the internet immediately.
  • Publishing online is also cheap. It requires only a modest computer, an editor and LaTeX or MathJax, all of which are either free, one-time purchases, or available from your university. (These days all these items are required for publishing a math book on paper or submitting an article to a paper journal as well as for publishing on the internet.)
  • Publishing online has the advantage that taking up more space does not cost more. I believe this is widely underappreciated. You can add comments explaining how you think about some type of math object, or about false starts that you had to abandon, and so on. If you want to refer to a diagram that occurs in another place in the paper, you can simply include a copy in the current place. (It took me much too long to realize that I could do things like that in abstractmath.org.)

Online journals

Many new online journals have appeared in the last few years. Some of them are deliberately intended as a way to avois putting papers behind a paywall. But aside from that, online journals speed up publication and reduce costs (not necessarily to zero if the journal is refereed).

A special type of online journal is the overlay journalG. A paper published there is posted on ArXiv; the journal merely links to it. This provides a way of refereeing articles that appear on ArXiv. It seems to me that such journals could include articles that already appear on ArXiv if the referees deem them suitable.

Types of mathematical communication

I wrote about some types of math communication in Mathematical Information I.

The paper Varieties of Mathematical Prose, by Atish Bagchi and me, describes other forms of communicating math not described here.

What mathematicians would like to know

Has this statement been proved?G

  • The internet has already made it easier to answer this query: Post it on MathOverflow or Math Stack Exchange.
  • It should be a long-term goal of the math community to construct a database of what is known. This would be a difficult, long-term project. I discussed it in my article The Mathematical Depository: A Proposal, which concentrated on how the depository should work as a system. Constructing it would require machine reading and understanding of mathematical prose, which is difficult and not something I know much about (the article gives some references).
  • An approach that would be completely different from the depository might be through a database of proved theorems that anyone could contribute to, like a wiki, but with editing to maintain consistency, avoid repetition, etc.

Known information about a conjecture

This information could include partial results.G An example would be Falting’s Theorem, which implies a partial result for Fermat’s Last Theorem: there is only a finite number of solutions of $x^n+y^n=z^n$ for integers $x, y, z, n$, $n\gt2$. That theorem became widely known, but many partial results never even get published.

Strategies for proofs

Strategies that are useful in a particular field.

The website Tricki is developing a list of such strategies.

It appears that Tricki should be referred to as “The Tricki”, like The Hague and The Bronx.

Note that there are strategies that essentially work just once, to prove some important theorem. For example, Craig’s Trick, to prove that a recursively enumerable theory is recursive. But of course, who can say that it will never be useful for some other theorem? I can’t think of how, though.

Strategies that don’t work, and whyG

The article How to discover for yourself the solution of the cubic, by Timothy Gowers, leads you down the garden path of trying to “complete the cubic” by copying the way you solve a quadratic, and then showing conclusively that that can’t possibly work.

Instructors should point out situations like that in class when they are relevant. A database of Methods That Work Here But Not There would be helpful, too. And, most important of all, if you run into a method that doesn’t work when you are trying to prove a theorem, when you do prove it, mention the failed method in your paper! (Remember: space is now free.)

Examples and Counterexample

I discovered these examples in twenty minutes on the internet.

Discussions

“Mathematical discussion is very useful and virtually unpublishable.”G But in the internet age they can take place online, and they do, in discussion lists for particular branches of math. That is not the same thing as discussing in person, but it is still useful.

PolymathG

Polymath sessions are organized attempts to use a kind of crowdsourcing to study (and hopefully prove) a conjecture. The Polymath blog and the Polymath wiki provide information about ongoing efforts.

Videos

  • Videos that teach math are used all over the world now, after the spectacular success of Khan Academy.
  • Some math meetings produce videos of invited talks and make them available on You Tube. It would be wonderful if a systematic effort could be made to increase the number of such videos. I suppose part of the problem is that it requires an operator to operate the equipment. It is not impossible that filming an academic lecture could be automated, but I don’t know if anyone is doing this. It ought to be possible. After all, some computer games follow the motions of the player(s).
  • There are some documentaries explaining research-level math to the general public, but I don’t know much about them. Documentaries about other sciences seem much more common.

References

The talks in Seattle

  • List of all the talks.

  • W. Timothy Gowers, How should mathe­matical knowledge be organized? Talk at the AMS Special Session on Mathe­matical Information in the Digital Age of Science, 6 January 2016.

  • Mathematical discussions, links to pages by Timothy Gowers. “Often [these pages] contain ideas that I have come across in one way or another and wish I had been told as an undergraduate.”
  • Colloquium notes

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exposition, language, math, understanding math

Mathematical Information I

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Introduction

The January, 2016 meeting of the American Mathematical Society in Seattle included a special session on Mathe­matical Information in the Digital Age of Science. Here is a link to the list of talks in that session (you have to scroll down a ways to get to the list).

Several talks at that session were about communi­cating math, to other mathe­maticians and to the general public. Well, that’s what I have been about for the last 20 years. Mostly.

Overview

These posts discuss the ways we communi­cate math and (mostly in later posts) the revolution in math communication that the internet has caused. Parts of this discussion were inspired by the special session talks. When they are relevant, I include footnotes referring to the talks. Be warned that what I say about these ideas may not be the same as what the speakers had to say, but I feel I ought to give them credit for getting me to think about those concepts.

Some caveats

  • The distinctions between different kinds of math communi­cation are inevitably fuzzy.
  • Not all kinds of communication are mentioned.
  • Several types of communication normally occur in the same document.

Articles published in journals

Until recently, math journals were always published on paper. Now many journals exist only on the internet. What follows is a survey of the types of articles published in journals.

Refereed papers containing new results

These communications typically containing proofs of (usually new) theorems. Such papers are the main way that academic mathematicians get credit for their researchG for the purpose of getting tenure (at least in the USA), although some other types of credit are noted below.

Proofs published in refereed journals in the past were generally restricted to formal proofs, without very many comments intended to aid the reader’s under­standing. This restricted text was often enforced by the journal. In the olden days this would have been prompted by the expense of publishing on paper. I am not sure how much this restriction has relaxed in electronic journals.

I have been writing articles for abstractmath.org and Gyre&Gimble for many years, and it has taken me a very long time to get over unnecessarily restricting the space I use in what I write. If I introduce a diagram in an article and then want to refer to it later, I don’t have to link to it — I can copy it into the current location. If it makes sense for an informative paragraph to occur in two different articles, I can put it into both articles. And so on. Nowadays, that sort of thing doesn’t cost anything.

Survey articles and invited addresses

You may also get credit for an invited address to a prestigious organi­zation, or for a survey of your field, in for example the Bulletin of the AMS. Invited addresses and surveys may contain considerably more explanatory asides. This was quite noticeable in the invited talks at the AMS Seattle meeting.

Books

There is a whole spectrum of math books. The following list mentions some Fraunhofer lines on the spectrum, but the gamut really is as continuous as a large finite list of books could be. This list needs more examples. (This is a blog post, so it has the status of an alpha release.)

Research books that are concise and without much explanation.

The Bourbaki books that I have dipped into (mostly the algebra book and mostly in the 1970’s) are definitely concise and seem to strictly avoid explanation, diagrams, pictures, etc). I have heard people say they are unreadable, but I have not found them so.

Contain helpful explanations that will make sense to people in the field but probably would be formidable to someone in a substantially different area.

Toposes, triples and theories, by Michael Barr and Charles Wells. I am placing our book here in the spectrum because several non-category-theorists (some of them computer scientists) have remarked that it is “formidable” or other words like that.

Intended to introduce professional mathematicians to a particular field.

Categories for the working mathematician, by Saunders Mac Lane. I learned from this (the 1971 edition) in my early days as a category theorist, six years after getting my Ph.D. In fact, I think that this book belongs to the grad student level instead of here, but I have not heard any comments one way or another.

Intended to introduce math graduate students to a particular field.

There are lots of examples of good books in this area. Years ago (but well after I got my Ph.D.), I found Serge Lang’s Algebra quite useful and studied parts of it in detail.

But for grad students? It is still used for grad students, but perhaps Nathan Jacobson’s Basic Algebra would be a better choice for a first course in algebra for first-year grad students.

The post My early life as a mathematician discusses algebra texts in the olden days, among other things.

Intended to explain a part of math to a general audience.

Love and math: the heart of hidden reality. by Edward Frenkel, 2014. This is a wonderful book. After reading it, I felt that at last I had some clue as to what was going on with the Langlands Program. He assumes that the reader knows very little about math and gives hand-waving pictorial expla­nations for some of the ideas. Many of the concepts in the book were already familiar to me (not at an expert level). I doubt that someone who had had no college math courses that included some abstract math would get much out of it.

Symmetry: A Journey into the Patterns of Nature, by Marcus du Sautoy, 2009. He also produced a video on symmetry.

My post Explaining “higher” math to beginners, describes du Sautoy’s use of terminology (among others).

Secrets of creation: the mystery of the prime numbers (Volume 1) by Matthew Watkins (author) and Matt Tweed (Illustrator), 2015. This is the first book of a trilogy that explains the connection between the Riemann $\zeta$ function and the primes. He uses pictures and verbal descriptions, very little terminology or symbolic notation. This is the best attempt I know of at explaining deep math that might really work for non-mathe­maticians.

My post The mystery of the prime numbers: a review describes the first book.

Piper Harron’s Thesis

The Equidistribution of Lattice Shapes of Rings of Integers of Cubic, Quartic, and Quintic Number Fields: an Artist’s Rendering, Ph.D. thesis by Piper Harron.

This is a remarkable departure from the usual dry, condensed, no-useful-asides Ph.D. thesis in math. Each chapter has three main parts, Layscape (explanations for nonspecialists — not (in my opinion) for nonmathe­maticians), Mathscape (most like what goes into the usual math paper but with much more explanation) and Weedscape (irrelevant stuff which she found helpful and perhaps the reader will too). The names of these three sections vary from chapter to chapter. This seems like a great idea, and the parts I have read are well-done.

These blog posts have useful comments about her thesis:

Types of explanations

Any explanation of math in any of the categories above will be of several different types. Some of them are considered here, and more will appear in Mathematical Information II.

The paper Varieties of Mathematical Prose, by Atish Bagchi and me, provides a more fine-grained description of certain types of math communication that includes some types of explanations and also other types of communication.

Images and metaphors

In abstractmath.org

I have written about images and metaphors in abstractmath.org:

Abstractmath.org is aimed at helping students who are beginning their study of abstract math, and so the examples are mostly simple and not at a high level of abstraction. In the general literature, the images and metaphors that are written about may be much more sophisticated.

The User’s GuideW

Luke Wolcott edits a new journal called Enchiridion: Mathematics User’s Guides (this link allows you to download the articles in the first issue). Each article in this journal is written by a mathematician who has published a research paper in a refereed journal. The author’s article in Enchiridion provides information intended to help the reader to understand the research paper. Enchiridion and its rationale is described in more detail in the paper The User’s Guide Project: Giving Experential Context to Research Papers.

The guidelines for writing a User’s Guide suggest writing them in four parts, and one of the parts is to introduce useful images and metaphors that helped the author. You can see how the authors’ user’s guides carry this out in the first issue of Enchiridion.

Piper Harron’s thesis

Piper Harron’s explanation of integrals in her thesis is a description of integrals and measures using creative metaphors that I think may raise some mathematicians’ consciousness and others’ hackles, but I doubt it would be informative to a non-mathematician. I love “funky-summing” (p. 116ff): it communicates how integration is related to real adding up a finite bunch of numbers in a liberal-artsy way, in other words via the connotations of the word “funky”, in contrast to rigorous math which depends on every word have an accumulation-of-properties definition.

The point about “funky-summing” (in my opinion, not necessarily Harron’s) is that when you take the limit of all the Riemann sums as all meshes go to zero, you get a number which

  • Is really and truly not a sum of numbers in any way
  • Smells like a sum of numbers

Connotations communicate metaphors. Metaphors are a major cause of grief for students beginning abstract math, but they are necessary for understanding math. Working around this paradox is probably the most important problem for math teachers.

Informal summaries of a proofW

The User’s Guide requires a “colloquial summary” of a paper as one of the four parts of the guide for that paper.

  • Wolcott’s colloquial summary of his paper keeps the level aimed at non-mathematicians, starting with a hand-waving explanation of what a ring is. He uses many metaphors in the process of explaining what his paper does.
  • The colloquial summary of another User’s Guide, by Cary Malkiewich, stays strictly at the general-public level. He uses a few metaphors. I liked his explanation of how mathematicians work first with examples, then finding patterns among the examples.
  • The colloquial summary of David White’s paper stays at the general-public level but uses some neat metaphors. He also has a perceptive paragraph discussing the role of category theory in math.

The summaries I just mentioned are interesting to read. But I wonder if informal summaries aimed at math majors or early grad students might be more useful.

Insights

The first of the four parts of the explanatory papers in Enchiridion is supposed to present the key insights and organizing principles that were useful in coming up with the proofs. Some of them do a good job with this. They are mostly very special to the work in question, but some are more general.

This suggests that when teaching a course in some math subject you make a point of explaining the basic techniques that have turned out very useful in the subject.

For example, a fundamental insight in group theory is:

Study the linear representations of a group.

That is an excellent example of a fundamental insight that applies everywhere in math:

Find a functor that maps the math objects you are studying to objects in a different branch of math.

The organizing principles listed in David White’s article has (naturally more specialized) insights like that.

Proof stories

“Proof stories” tell in sequence (more or less) how the author came up with a proof. This means describing the false starts, insights and how they came about. Piper Harron’s thesis does that all through her work.

Some authors do more than that: their proof stories intertwine the mathe­matical events of their progress with a recount of life events, which sometimes make a mathe­matical difference and sometimes just produces a pause to let the proof stew in their brain. Luke Wolcott wrote a User’s Guide for one of his own papers, and his proof story for that paper involves personal experiences. (I recommend his User’s Guide as a model to learn from.)

Reports of personal experiences in doing math seem to add to my grasp of the math, but I am not sure I understand why.

References

The talks in Seattle

  • List of all the talks.

  • W. Timothy Gowers, How should mathe­matical knowledge be organized? Talk at the AMS Special Session on Mathe­matical Information in the Digital Age of Science, 6 January 2016.
  • Colloquium notes. Gowers gave a series of invited addresses for which these are the notes. They have many instances of describing what sorts of problems obstruct a desirable step in the proof and what can be done about it.

  • Luke Wolcott, The User’s Guide. Talk at the AMS Special Session on Mathe­matical Information in the Digital Age of Science, 6 January 2016.

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