RIP Mitchell Feigenbaum (1944–2019)

Mathematical physicist Mitchell Feigenbaum, known for his work on the period-doubling route to chaos in the logistic map and other nonlinear phenomena, died over the weekend.

Here is his wikipedia page.

Update (7/18/19): Today, The New York Times published an obituary of Feigenbaum. The first picture in it is fantastic!

Update (7/23/19): Here is a very nice blog entry by Stephen Wolfram about Feigenbaum, his constant, and other bits of Feigenbaum's history.)

812 Double Pendulums with Different Initial Conditions

This is what 812 double pendulums with different initial conditions look like https://t.co/jklEvfb5EI | https://t.co/ctsPCmFfEJ pic.twitter.com/jMar6rlRma

— Massimo (@Rainmaker1973) October 26, 2018

"Hyperchaos" in the White House

I saw "CHAOS" trending on Twitter this morning, so I automatically looked it up, before seeing that it was about politics and then moving on to something else.

And now I see this article, which predominantly consists of an interview with nonlinear dynamicist (and pioneer of chaos) Jim Yorke, including discussions about both mathematical chaos and hyperchaos.

Here is how the part with Yorke begins: "That's not chaos, according to James A. Yorke, Distinguished University Professor of Mathematics and Physics at the University of Maryland at College Park." It goes on from there.

Just think about it: Jim Yorke, an expert in chaotic dynamics, was interviewed by CNN about Donald Trump, precisely because of the former's expertise in mathematical chaos. Yup, we've gone full Illuminati.

(Tip of the cap to Bruno Eckhardt and fuzzy sweatshirt particle.)

Headline: "Massive Wave of Butterflies Lights Up Denver Weather Radar"

How very chaotic. :)

At least the radar wasn't jammed.

(Tip of the cap to Ioana Marilena.)

But Can We Set the Lyapunov Exponent?

Apparently, there is a microwave with a 'CHAOS' mode (in all caps).

I have only one question: Are we allowed to set the Lyapunov exponent? (Technically, I am thinking of the maximum one.)

why does my microwave have a CHAOS MODE pic.twitter.com/feV8M6uxQx

— aoife (@AoifeeO) September 12, 2017

(Tip of the cap to George Takei.)

Update: It looks like chaotic dynamics actually are explicitly involved. (Tip of the cap to Melvin Leok for the link.)

Update 2: Following up on Melvin's comment, I did some googling and found this article. I still haven't figured out which system they used. I suppose I should treat this like the chaotic water wheels. The people who designed this option could have chosen any one of the standard models.

Update 3: Bah. The relevant reference is in a conference proceeding whose parent domain is dead (probably long dead). I might actually have to use a physical library to determine decisively which system was used. (Jaroslav Stark, one of the authors of the above perspective piece, died several years ago. I could potentially see if his coauthor, who I have never heard of, is reachable. The names of the authors of that conference proceeding are going to defy Google.)

The Masque of the Chaotic Attractor

When you want to go to The Masquerade, but the only masque you have is a Lorenz attractor.

(Thanks to Juan Restrepo for the composition.) pic.twitter.com/QNB7O912vH

— Mason Porter (@masonporter) September 1, 2017

(This could, however, work very well at Dynamics Days.)

Together, Mathematicians and Lepidopterologists Will Rule the World!

Follow me! Follow me to freedom!

Long Live the Matlab Billiard Simulator!

A couple of undergrads, Caitlin Keady and Sam King (who were in an REU and worked with my fellow former Georgia Tech postdoc Mark Demers for a summer project at Fairfield University), decided to update our old billiard simulator to be compatible with the 2016a release of Matlab. (I used it successfully on the 2016b release of Matlab.) They also added both new examples and new types of plots. You can download their version from the Matlab file exchange website.

Some people have still been using this software even though it's been 12 years since our original release—my former undergrad Steven Lansel did this in one of the first undergrad projects I supervised, and in 2006 on Kris Kazlowski updated the software—and even though things had gotten to the point that they were required to use a several-year-old version of Matlab. But now the billiard simulator is up-to-date again!

We certainly didn't think that people would still be using our software so many years later.

Love, Three-Body Problems, and Chaos

Well, mathematicians certainly like to discuss love and its chaotic implications. (Remember, the three-body problem is provably chaotic.)

XKCD on Chaos: "Can You Do That Weird Laugh?"

The topic for today's XKCD is chaos, which is of course near and dear to my heart. I love the mouseover: "Although the oral exam for the doctorate was just 'can you do that weird laugh?'"

Hmmm... I got my PhD in quantum chaos, and I never got that question on my oral exam to defend my thesis. :(

RIP Richard L. Liboff (1931–2014)

Steve Strogatz just e-mailed me to let me know that Richard Liboff, my PhD supervisor, has died. The obituary only came out yesterday, but Richard died on 9 March. The comment, which is recalled in the Cornell obituary, that Richard made about his book in the Spiderman movie was quintessentially him. (I remember that incident when Cornell first had a press release about it.)

Richard seemed pretty crazy at times (though, to be honest, I bet that my students would say the same thing about me!), and we ultimately had a falling out (and I couldn't get him to respond to e-mails after fall 2003 or early 2004), but I do have a soft spot for him --- and I have some of my own stories to tell, of course. Richard was quite a character, and Cornell's obituary conveys it very well. In some ways, this is like the closing of a final bit of my graduate-school chapter, although I still have strong contacts with many of the Cornell faculty.

Here is a link to Richard's wikipedia page. He is best known for his quantum mechanics book, of course. (Given how well-known his book is, I'm rather surprised that his obituary hasn't circulated much more widely. It certainly deserves to be. Through his textbooks, Richard made extremely important expository contributions to generations of young physicists and other scientists.)

I published my first science paper jointly with Richard. It is nowhere near my best paper, but it will always be my first one.

Update (5/25/14): I noticed that this blog entry was getting several hits, so I tried to figure out the mechanism via Google (no luck yet). In the process, though, I found something really interesting that I never knew: Richard self-published a novel! (Given the details of the Amazon page, I am assuming that it was self-published.)

Yakov Sinai Wins Abel Prize

We've got a win for the home team (aka: dynamical systems) today: Yakov ("Yasha") Sinai has won the Abel Prize!

This is richly deserved. And if you look at this last page and know my academic interests, you'll see many subjects that are near and dear to my heart --- like dynamical systems, billiards, chaos, etc.

A few years ago, I tried to get Yasha interested in the two-particle billiards on which I have worked a bit with Bunimovich and a couple of students. He brought up some very good ideas, obviously, but he didn't seem super interested in the problem.

Also, as far as mathematical lineage goes, this one is a big win for the home team in a very large sense (well beyond dynamical systems). Besides having worked on billiard problems, there is pretty direct lineage: my official postdoc mentor at Georgia Tech was Leonid ("Lyonia") Bunimovich, who was a PhD student of Sinai.

Update: Here is the blurb in Nature News.


Update (4/10/14): There is now an article about Sinai's Abel Prize in The Daily Princetonian. I love Lyonia's quote in the article (because it's typical Lyonia): "I was waiting for this event already for some years."

Pictures and Vampires in Paris

Here are my initial pictures from Paris from today and last night. (Most of them are from today.)

Notice the Theatre du Chaos on Rue Henri Poincaré. I approve! The street is a dinky little residential street, and I was very pleased indeed to see this local theatre in one of its corner. It made me really happy.

I just noticed on Google Maps that Paris has a Vampire Museum not far from Rue Henri Poincaré. Too bad I only noticed that after walking all the way back instead of when I was there a couple of hours ago... I think there is a decent chance it's not open today anyway, but let's see if I can figure out from here when it's open. You can also find some information on another page from the Atlas Obscura website

And here is how to make an appointment to visit the museum (it's by appointment only). I have to admit that I am very tempted to do try to make one, but I would rather look around in there without talking to someone while I am doing it, so I'm likely not going to do it. This is the type of thing I'd like to go and do with a friend. :)

An Aural Poincaré Section

This musical creation seems to essentially amount to an aural representation of a Poincaré section of the dynamics of a triple pendulum (though the description provided with the video is a bit hard to parse, so I am not 100% sure that this is precisely a legitimate Poincaré section).

(Tip of the cap to whoever posts for Physics Today on Facebook.)

Update: Here is a different aural Poincaré section of a triple pendulum.

Children + Taxes Implies Chaos

Yes, really. And this new paper (which is called Child Allowances, Fertility, and Chaotic Dynamics) claims to prove this in a model using rigorous mathematics. Obviously, this depends on how much one believes the model. The paper is written in a rather abstract manner, so clearly I am skeptical.

There are some "awesome" things in the article, however. For one thing, I am not sure how chaotic dynamics is important to the problem at hand (as opposed to just in the model the authors happen to study), but chaos is genuinely important in other applications, so who knows? Another big "win" is the use of the term "allowance". What the authors have in mind is the number of children that one is allowed to have, but the other (unintended) interpretation of parents giving a child an "allowance" with which to buy things is what truly makes this a thing of beauty. I didn't look carefully enough at the mathematics itself, so I have no opinion on that. Rather, I am viewing this through my mathematical modelling lens, and I think it is "awesome" from that perspective. And the article title is truly a thing of beauty!

This is the type of article that makes me both laugh and cry --- and I think that there might be an Ig Nobel Prize in store for the authors of this paper.

"Oscillate Wildly"

I just found out (and listened to) the song "Oscillate Wildly" by The Smiths. The title alone makes this awesome. It's actually a rather good instrumental, but the scientific things that the title automatically brings to mind is what makes this awesome.

A Toast to Poincaré!

Henri Poincaré died 100 years ago today. (Poincaré is the founding father of my field.)

(Tip of the cap to Physics Today.)

One of My Contributions to Physics

The quote "Cycles. Is there anything they can’t do?" certainly sounds like something that I would say or write sarcastically, though I no longer remember when I said (or wrote) this. Anyway, you can find it at the top of Chapter 13 of Chaos: Classical and Quantum.

Fun Fact about OCD

Fun Fact: I chose the name for my research group because it allows me to use the acronym "OCD" for my group. Yes, that is the actual reason.

Precedent (and partial inspiration): The University of Maryland's "Chaos Group" includes a lot of research on nonlinear systems, complex systems, and networks. Just like me.

Takes from the ArXiv: Modelling Roulette

There is a new paper on the arXiv preprint server that models outcomes in Roulette. This might be of interest to several of you. I can certainly think of people in OCIAM who I think would get a kick out of this problem.

(Tip of the cap to whoever does the Facebook posts for Physics Today.)