The Spring semester is now well underway! This means it’s time for the Bay Area Mathematical Artists to begin meeting. This weekend, we had our first meeting of 2018 at the University of San Francisco.

As usual, we began informally at 3:00, giving everyone plenty of time to make it through traffic and park. This time we had three speakers on the docket: Frank A. Farris, Phil Webster, and Roger Antonsen.

Frank started off the afternoon with a brief presentation, giving us a teaser for his upcoming March talk on *Vibrating Wallpaper*. Essentially, using the complex analysis of wave forms, he takes digital images and creates geometrical animations with musical accompaniment from them. A screenshot of a representative movie is shown below:

You can click here to watch the entire movie. More details will be forthcoming in the next installment of the Bay Area Mathematical Artists (though you can email him at ffarris@scu.edu if you have burning questions right now). Incidentally, the next meeting will be held at Frank’s institution, Santa Clara University; he has generously offered to host one Saturday this semester as we have several participants who drive up from the San Jose area.

Our second speaker was Phil Webster, whose talk was entitled *A Methodology for Creating Fractal Islamic Patterns.* Phil has been working with Islamic patterns for about five years now, and has come up with some remarkable images.

Here, you can see rings of 10 stars at various levels of magnification, all nested *very* carefully within each other. While it is fairly straightforward to iterate this process to create a fractal image, a difficulty arises when the number and size of rosettes at a given level of iteration are such that they start overlapping. At this point, a decision must be made about which rosettes to keep.

This decision involves both mathematical and artistic considerations, and is not always simple. One remark Phil hears fairly often is that he’s actually creating a model of the hyperbolic plane, but this is in fact *not* the case. Having sat down with him while he explained his methodology to me, I can attest to this fact. His work may be visually somewhat reminiscent of the hyperbolic plane, but the mathematics certainly is not.

Moreover, in addition to creating digital prints, Phil has also experimented with laser cutting Islamic patterns, as shown in the intricate pieces below.

If you would like to learn more about Phil’s Islamic fractal patterns, feel free to email him at phil@philwebsterdesign.com.

We ended with a talk by Roger Antonsen, *From Simplicity to Complexity.* Roger is giving a talk at the Museum of Mathematics in New York City next month, and wanted a chance to try out some ideas. He casually remarked he had 377 slides prepared, and indicated he needed to perhaps trim that number for his upcoming talk….

Roger remarked that as mathematicians, we know on a hands-on basis how very simple ideas can generate enormous complexity. But how do you communicate this idea to a general audience, many who are children? This is his challenge.

The idea of this “tryout” was that Roger would share some of his ideas with us, and we would give him some feedback on what we thought. One idea that was very popular with participants was a discussion of Langton’s ant. There are several websites you can visit — but to see a quick overview, visit the Wikipedia page.

The rules are simple (as you will already know if you googled it!). An ant starts on a grid consisting totally of white squares. If the ant is on a white square, it turns right a quarter-turn, moves ahead one square, and the square the ant was on turns to black. But if the ant is on a black square, it turns left a quarter-turn, moves one unit, and the square the ant was on turns to white.

It seems like a fairly simple set of rules. As the ant starts moving around, it seems to chaotically color the squares black and white in a random sort of pattern.

The image above shows the path of the ant after 11,000 steps (with the red pixel being the last step). Notice that the path has started to repeat, and continues to repeat forever!

Why? No one really knows. Yes, we can see that it actually *does* repeat, but only sometime after 10,000 *apparently* random steps. The behavior of this system has all of a sudden become very mysterious, without a clear indication of *why.*

If the rules for moving the ant always resulted in just random-looking behavior, perhaps no one would have looked any further. But there are so many surprises. Especially since there is no reason you have to stick to the rules above. As suggested in the Wikipedia article, you can add more colors, more rules, and even more ants….

For example, consider the set of rules in the following image. It should be relatively self-explanatory by now: there are four colors; if the ant is on a black square, turn right a quarter-turn and move forward one unit, then change the color of the square the ant was on to white; then continue (where green squares becomes black, in cyclic order).

This looks like a cardiod! And if you actually zoom in enough, you’ll see that this is the image after 500,000,000 iterations…though again, no one has the slightest idea *why* this happens. Why should a simple set of rules based on 90° rotations generate a cardioid, of all things?

From the simple to the complex! This was only one of literally dozens of topics Roger was able to elaborate on — and he illustrated each one he showed us with compelling images and animations. For more examples, please see his web page, or feel free to email him at rantonse@ifi.uio.no. You can also see the announcement for his MoMath talk here.

As usual, we went our for dinner afterwards, this time for Thai. It seems that no one wanted to leave — but some of the participants had a 90-minute drive ahead of them, so eventually we had to head home. Stay tuned for the summary of next month’s meeting, which will be at Santa Clara University!

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