What Happens in Davis Stays in Davis

I am going to take a cab to the Fremont Amtrak station and then a train to Davis, where I will be giving a talk in UC Davis's math department. This is the first time I have visited UC Davis since I interviewed for a job there in 2005. Tomorrow, I will be having breakfast with a cousin who is a PhD student in biology and then talking to some of the networks people.

Also: I left on Friday night to go hang out with peeps in San Francisco. I am now back in Palo Alto, but tomorrow I fly to the UK to spend a week in Oxford.

"Report: Cops Look for Sausage"

Well, the Italian Sausage has gone AWOL.

You know, I really hope that Randall Simon is somehow involved. That would rock! (And in case you're wondering, Simon's claim to fame is this incident.)

Update (2/28/13): Well, the missing link has now been found. This article includes the following superb line: Bartender Jen Mohney told the Milwaukee Journal Sentinel that two men -- one wearing a hoodie pulled over his face -- brought the $3,000, 7-foot-long Italian Sausage costume into the bar, dropped it onto a stool and told her, "You did not see anything." Seriously, that ought to be the first line of a novel!

I'm... Too Sexy For This List... Too Sexy For This List...

Business Insider has published its list of the 50 sexiest scientists.

To paraphrase Right Said Fred: I'm... too sexy for this list. Too sexy for this list...*

* Full disclosure: I have not yet actually looked at the list.

Lloydies from my era should read that list with visuals from a certain airband skit, of course! :)

(Tip of the cap to Kevin Hickerson.)

Ancient d20

Oh, wow! Ancient Egyptians were apparently rolling 20-sided dice. That is incredibly awesome!

(Tip of the cap to Game Empire of Pasadena.)

Archives of Dragon Magazine are Online

The archives of Dragon magazine are online. Very cool! (This is a very nice resource for role-playing.)

(Tip of the cap to Andy Sayer.)

Today's Fortune: My "Emotional Currents are Flowing"

I just got the following fortune today: "Your emotional currents are flowing powerfully now [in bed]."

I guess "emotional currents" is what people call such things nowadays. Quite the euphemism, though this is more of a "fortune" than a fortune.

And, for the second time in 3 days, a fortune cookie is inviting me to learn the Chinese word for pumpkin.

"Multi-Stage Complex Contagions"

I just blogged about my new paper on billiards, which just got published in final form today in Chaos. Well, the very next article in the journal, which was (unsurprisingly, given these statements) also published today, is my new paper on modelling social influence. Here are the details for that paper.

Title: Multi-Stage Complex Contagions

Authors: Sergey Melnik, Jonathan A. Ward, James P. Gleeson, and Mason A. Porter

Abstract: The spread of ideas across a social network can be studied using complex contagion models, in which agents are activated by contact with multiple activated neighbors. The investigation of complex contagions can provide crucial insights into social influence and behavior-adoption cascades on networks. In this paper, we introduce a model of a multi-stage complex contagion on networks. Agents at different stages --- which could, for example, represent differing levels of support for a social movement or differing levels of commitment to a certain product or idea --- exert different amounts of influence on their neighbors. We demonstrate that the presence of even one additional stage introduces novel dynamical behavior, including interplay between multiple cascades, which cannot occur in single-stage contagion models. We find that cascades—and hence collective action—can be driven not only by high-stage influencers but also by low-stage influencers.


Fun Fact: This might be the first published mathematics paper that uses the word "hipster". You should click on the link and see how we use it. :)

"Two-Particle Circular Billiards Versus Randomly Perturbed One-Particle Circular Billiards"

My first paper on billiards since 2006 has just been published in final form. Here are the details.

Title: Two-Particle Circular Billiards Versus Randomly Perturbed One-Particle Circular Billiards

Authors: Sandra Ranković and Mason A. Porter

Abstract: We study a two-particle circular billiard containing two finite-size circular particles that collide elastically with the billiard boundary and with each other. Such a two-particle circular billiard provides a clean example of an “intermittent” system. This billiard system behaves chaotically, but the time scale on which chaos manifests can become arbitrarily long as the sizes of the confined particles become smaller. The finite-time dynamics of this system depends on the relative frequencies of (chaotic) particle-particle collisions versus (integrable) particle-boundary collisions, and investigating these dynamics is computationally intensive because of the long time scales involved. To help improve understanding of such two-particle dynamics, we compare the results of diagnostics used to measure chaotic dynamics for a two-particle circular billiard with those computed for two types of one-particle circular billiards in which a confined particle undergoes random perturbations. Importantly, such one-particle approximations are much less computationally demanding than the original two-particle system, and we expect them to yield reasonable estimates of the extent of chaotic behavior in the two-particle system when the sizes of confined particles are small. Our computations of recurrence-rate coefficients, finite-time Lyapunov exponents, and autocorrelation coefficients support this hypothesis and suggest that studying randomly perturbed one-particle billiards has the potential to yield insights into the aggregate properties of two-particle billiards, which are difficult to investigate directly without enormous computation times (especially when the sizes of the confined particles are small).

New Punctuation Marks

Here are eight new punctuation marks for you to use and abuse. A couple of them are awesome. Sadly, they missed to 'bidirectional semicolon' :: (which I saw discussed in an awesome short play whose mechanism of delivering its premise was a seminar in which the speaker introduced many new punctuation marks that were heretofore missing), in which the left side explains the right side and vice versa. The example used in the play was "To be a Jew :: To be a Jew".

(Tip of the cap to Meredith Alden for the website.)

Jose Canseco's Theory of Gravity

Jose Canseco promised his thoughts on gravity and then he delivered his theory of gravity in a sequence of Twitter posts.

Wow. Why didn't I think of that explanation?

Comedy Gold.

(Tip of the cap to Rob Neyer.)

"Dark Solitary Waves in a Class of Collisionally Inhomogeneous Bose-Einstein Condensates"

A new paper of mine just got published in final form today. It's my first paper on Bose-Einstein condensates since 2008 (or, as Georg Gottwald called it, "a relapse"). Anyway, here are the details.


Title: Dark Solitary Waves in a Class of Collisionally Inhomogeneous Bose-Einstein Condensates

Authors: Chang Wang, Kody J. H. Law, Panayotis G. Kevrekidis, and Mason A. Porter

Abstract: We study the structure, stability, and dynamics of dark solitary waves in parabolically trapped, collisionally inhomogeneous Bose-Einstein condensates (BECs) with spatially periodic variations of the scattering length. This collisional inhomogeneity yields a nonlinear lattice, which we tune from a small-amplitude, approximately sinusoidal structure to a periodic sequence of densely spaced spikes. We start by investigating time-independent inhomogeneities, and we subsequently examine the dynamical response when one starts with a collisionally homogeneous BEC and then switches on an inhomogeneity either adiabatically or nonadiabatically. Using Bogoliubov-de Gennes linearization as well as direct numerical simulations of the Gross-Pitaevskii equation, we observe dark solitary waves, which can become unstable through oscillatory or exponential instabilities. We find a critical wavelength of the nonlinear lattice that is comparable to the healing length. Near this value, the fundamental eigenmode responsible for the stability of the dark solitary wave changes its direction of movement as a function of the strength of the nonlinearity. When it increases, it collides with other eigenmodes, leading to oscillatory instabilities; when it decreases, it collides with the origin and becomes imaginary, illustrating that the instability mechanism is fundamentally different in wide-well versus narrow-well lattices. When starting from a collisionally homogeneous setup and switching on inhomogeneities, we find that dark solitary waves are preserved generically for aligned lattices. We briefly examine the time scales for the onset of solitary-wave oscillations in this scenario.

What Happens in Chapel Hill Stays in Chapel Hill

I am now in Chapel Hill, North Carolina to visit my collaborator Peter Mucha at University of North Carolina. I will also be giving their applied mathematics colloquium on Friday.

And to describe dinner at the hotel restaurant tonight, let me just mention the following: Douchebags are drawn to sports bars like moths to a flame. [[...groan...]]

Tales from the ArXiv: Baby Names and Random Walks

Well, how about that: using things like PageRank and other random-walk algorithms to come up with baby names. It's crazy, but I kind of dig it. :) Also, I these somebody wants an Ig Nobel prize (in Peace?)...

You can try it for yourself at the Nameling website.

Sacrificing Privacy in Order to Referee a Paper?

Maybe I am just in an ornery mood this morning, but I don't think I should have to sign an annoying web privacy policy when I am being asked to provide my services for free to a journal. Here is part of what I wrote to the editor who had the misfortunate to ask for my refereeing services (and to get my name wrong, for that matter):

"The JStat website forces one to actively agree to an insidious 'privacy' policy to use it. (This is the first page one gets when logging in.) Refereeing is something academics do as a service and I am content to do my duty just like everyone else, but I am not going to sign such a policy in order to do it. I have signed such things in other contexts, but that is when I am receiving the service --- not providing it. Accordingly, please do not ever ask me to referee a paper again. I suggest recommending to the journal that they change how they do things."

The interesting thing is that if I ever submit there, then I suppose I would be agreeing to it, but now I am going to think twice if I ever consider submitting there. (I'm not saying I won't do it, but I would think harder about it than I would have otherwise.)

(And, while you're at it, get off my damn lawn!)

By the way, the offending journal is Journal of Statistical Mechanics. Maybe it's just how they presented this that really irked me? The other journals probably all have something like this as well.

APS is Going to Kathmandu?

The American Physical Society seems to have farmed out is page proof productions to a company whose employees are e-mailing me from the +0530 timezone --- I didn't know that fractional timezones even existed! They do, and this appears to be Nepal. I guess the APS is pulling a Bob Seger? (I hope somebody understands this reference without looking it up.) Excuse the cynicism, but this is making me think of the customer service stuff.

Importantly, the people working on the page proof of my article that I have in mind have been very fast and efficient about things, but I still find this to be a bit strange.

Update: Alan Champneys tells me that +0530 covers much of India.

Profiling?

A funny thing happened on the way back from campus...

I was walking from campus to the bus station when a police officer pulled me aside and said he wanted to talk to me. He explained that there had been an Asian male who had spent an inordinately large amount of time in a bathroom on campus and that I somewhat matched his description. (What?)

So I explained to him that I was a mathematician and that I was going home from a seminar, and he let me go.

I think that I played the 'mathematician' card to get out of trouble rather than the 'not Asian' card out of pure instinct (or perhaps reflex).

I almost never actually try to get into trouble, but I really have developed a strange knack for getting into these types of situations.

P.S. And it gets better. This was Officer Lee (who had some Asian features but wasn't obviously Asian) who stopped me to have a word with me.

I think that this story really has to become part of my legend---especially because it's 100% true.

How to Woo a Scientist

Here is some published advice for how to woo a scientist.

Here is one excellent quote from the article: Scientists are also typically stood alone in a social environment, looking quite fearful. It's OK to approach them, but do so slowly and calmly, and if possible hold your hands out, palms open and facing upwards, to emphasise that you pose no threat.

And here is another one: If you do manage to strike up an initial dialogue with a scientist, it's important to keep things going. Should the conversation falter or hit a lull, try asking the question "How is your grant application going?"

(Tip of the cap to Alex Cayco-Gajic.)

Awesome Google Doodle!

Today's (Feb 14) Google Doodle is superb! It honors both Valentine's Day and George Ferris. It is also interactive, and you can see different pairs of animals go out on dates. The fox is pretty damn funny, and the date between the bear and the octopus is hilarious. I approve!

Mathematicians and OCD

No, mathematicians do not have OCD. Not at all.

P.S. I am guilty as charged. (And for what it's worth, I actually find the idea in this article to be interesting.)

Ambiguous Fortune Cookie

"The world will soon be ready to receive your talents [in bed]."

The two possible meanings are pretty different from each other (though they do overlap a little bit).

This Space Left Intentionally Blank

For the second time in my blog's history, I have deleted one of my posts. I am happy to talk about this offline. (I think I am becoming more sensitive with age, which is a good thing.)

Actually, "sensitive" isn't the right word; I have always been very sensitive. I am thinking of sudden bouts of empathy being somewhat more common than they used to be. (Empathy is difficult for me unless I know somebody well, and even then it often challenges me.) You can thank some of my good friends for that!

Tales from the ArXiv: Heavy Metal Edition

I just saw a new paper on the arXiv that looks like it will be a promising contender for an Ig Nobel Prize.

Title: Collective Motion of Moshers at Heavy Metal Concerts

Authors: Jesse L. Silverberg, Matthew Bierbaum, James P. Sethna, Itai Cohen

Abstract: Human collective behavior can vary from calm to panicked depending on social context. Using videos publicly available online, we study the highly energized collective motion of attendees at heavy metal concerts. We find these extreme social gatherings generate similarly extreme behaviors: a disordered gas-like state called a mosh pit and an ordered vortex-like state called a circle pit. Both phenomena are reproduced in flocking simulations demonstrating that human collective behavior is consistent with the predictions of simplified models.


Bonus:This paper, entitled Data Mining of the Concept "End of the World" in Twitter Microblogs (but do the authors feel fine?), also seems like it might be a legitimate contender.

Separated at Birth?

Separated at Birth: preppy Tim Lincecum (baseball player) and preppy Rob Ghrist (mathematician).

By contrast, here are Tim Lincecum and Rob Ghrist with long hair.

Novel Strategy for Proving Theorems

Seriously, whispering to yourself while using a urinal in a public restroom is creepy. (I am in Stanford's math building right now.)

Maybe this is how this guy proves his most important theorems?

Oh, Rats!

I find this SMBC much funnier now than I would have in the past now that I have been reading neuroscience papers with rats.

The Derivator

Algebraist: "You don't want the full definition of derivator. It would take five journal pages."

Me [after conversation about this continues among others for a bit]: "I think it would be fine to have a five-page article for the definition as long as it includes a picture of The Terminator."

Quote of the Day: Money Edition

My quote of the day actually occurred yesterday. I was going to lunch with some Rutgers people (and one of my fellow visitors, who I know and was very surprised to see yesterday), but I had forgotten to bring money or a credit card with me. I had my wallet in my computer bag at the time, so I suddenly exclaimed something like "Oh! I need to go to my computer to get some money." This didn't make too much sense to anybody besides me, and the deadpan response I got of "Do you also need a printer?" was absolutely priceless.

Old Baseball

Now that is an old baseball. And it's also way cool.

Sudden Insight

Insight: "One more reference letter" is just like "one more turn". This stuff is for very good causes and I am happy to help people (and will of course continue to help people in this way when I am a relevant person to do so), but sigh...

There are so many things in my life that paper-cut me to death at times.

I know, I know: For some people, this is also known as "payback".

What Happens in New Brunswick Stays in New Brunswick

I am now visiting Rutgers for a few days to give a talk and to have good discussions about computational homology, data, and networks (and probably other things too). I am being hosted by Konstantin Mischaikow, who I know from my Georgia Tech years.

"(And Applied)"

More trips down Memory Lane...

I walked by Thurston. At the front of the building, if you look carefully, you can still notice the remnants of the parentheses that someone once snarkily put around "and Applied" in "Theoretical and Applied Mechanics". (Those parentheses were there for at least 2-3 years.) Now, the department no longer even exists.

Also, when I was walking back to campus from Collegetown, without thinking I took my old route that would take me directly back to Rhodes Hall and had to stop myself from walking all the way there.

Well Played

It turns out that sometimes you have to be very careful about what you write in the acknowledgements (and biography and preface and the like) of your PhD thesis, because it might come back to haunt you.

When I was finishing up in 2002, I had decided that because that was the only part of a thesis that most people read that I would have some fun in it and put easter eggs of various sorts to amuse my friends and future students (and in general to just be playful with it).

Well, today the introduction right before my colloquium was a bit unusual---and not like any other speaker introduction I have ever witnessed in my career thus far. With some help from the current CAM students (actually, my understanding is that it was their idea), some of my words from that part of my thesis were taken out and used for my introduction instead of doing the usual career path and honors that are typical in such things. My host's flight was cancelled and he could only make it for dinner and had to miss the seminar, and Peter Frazier did the introduction and was thus the MC for the shenanigans. (Peter is now a faculty member at Cornell and was my classmate in Lloyd House back in the day at Caltech.)

Wow. This caught me completely by surprise. Well played. Very well played.

And I probably deserved it. :)

P.S. Some of these CAM students specifically looked up and listened to "Tarzan Boy" just to see what on earth I was talking about in that document!

The Fouriest Transform

Really! A Fourier transform is a transform that has 4 occurring more often in it.