The Fluid Dynamics of Sheep

By the way, sheep are a fluid.

Also see one of my previous blog entries.

National Videogame Museum to Open in April

I want to take a field trip to the new U.S. National Videogame Museum, which will open in Frisco, Texas in April.

Even more than that, I want to go to the classic arcade and American Classic Arcade Museum at Funspot in New Hampshire.

(Tip of the cap to Paul Carter for news about the new museum.)

"Superdiffusive Transport and Energy Localization in Disordered Granular Crystals"

A new paper of mine just came out in final form today. Here are the details. (Also see a paper by others published as a consecutive article with ours. Scientifically, it's really good that these articles have appeared as back-to-back papers.)

Title: Superdiffusive Transport and Energy Localization in Disordered Granular Crystals

Authors: Alejandro J. Martínez, P. G. Kevrekidis, and Mason A. Porter

Abstract: We study the spreading of initially localized excitations in one-dimensional disordered granular crystals. We thereby investigate localization phenomena in strongly nonlinear systems, which we demonstrate to differ fundamentally from localization in linear and weakly nonlinear systems. We conduct a thorough comparison of wave dynamics in chains with three different types of disorder—an uncorrelated (Anderson-like) disorder and two types of correlated disorders (which are produced by random dimer arrangements)—and for two types of initial conditions (displacement excitations and velocity excitations). We find for strongly precompressed (i.e., weakly nonlinear) chains that the dynamics depend strongly on the type of initial condition. In particular, for displacement excitations, the long-time asymptotic behavior of the second moment ˜m2 of the energy has oscillations that depend on the type of disorder, with a complex trend that differs markedly from a power law and
which is particularly evident for an Anderson-like disorder. By contrast, for velocity excitations, we find that a standard scaling m_2 ∼ t^γ (for some constant γ) applies for all three types of disorder. For weakly precompressed (i.e., strongly nonlinear) chains, m_2 and the inverse participation ratio P^{−1} satisfy scaling relations m_2 ∼ t^γ and P^{−1} ∼ t^{−η}, and the dynamics is superdiffusive for all of the cases that we consider. Additionally, when precompression is strong, the inverse participation ratio decreases slowly (with η < 0.1) for all three types of disorder, and the dynamics leads to a partial localization around the core and the leading edge of a propagating wave packet. For an Anderson-like disorder, displacement perturbations lead to localization of energy primarily in the core, and velocity perturbations cause the energy to be divided between the core and the leading edge. This localization phenomenon does not occur in the sonic-vacuum regime, which yields the surprising result that the energy is no longer contained in strongly nonlinear waves but instead is spread across many sites. In this regime, the exponents are very similar (roughly γ ≈ 1.7 and η ≈ 1) for all three types of disorder and for both types of initial conditions.

Gravitational Waves have been Observed Directly

You can read about it here.

And thanks to Aaron Clauset and YY Ahn for posting an explanation from PhD Comics for how gravitational waves work (and the approach used in LIGO to observe them directly for the first time).

Here is a link to the CNN.com's article reporting the discovery.

Valentine's Day and Taking Limits

Here is an SMBC Comics with a Valentine's twist.

40th Birthday

Yesterday I turned 40. It happens to everybody (unless they die at a younger age, of course).

My research group banded together to give me a birthday present at Networks Journal Club today!

First, we have a multilayer network of (most) current members and several former members of my group. In fact, it is an induced subgraph, with me as the ego node. (If you take a look, it seems like one should ponder a bit about how to define an induced subgraph in a multilayer context.) The layers are defined by membership in Somerville College, coauthorship of papers, and Facebook friendship. (There are no interlayer edges, so technically this is an edge-colored multigraph.) Today’s talk included some calculations on this network.

Second, they bought me a plush ankylosaurus (aka: best dinosaur ever!), and some of my students noticed that that was the type of plush dinosaur I really wanted to get as a child but never actually saw in a store.

Instant Thesis Topic for Philosophy

Just follow the tip in today's SMBC.

Mary Somerville to Appear on Scottish £10 Note!

Mary Somerville will appear on a new £10 note from the Royal Bank of Scotland. Excellent!

(Tip of the cap to Alice Prochaska.)

Networks and Physics Subject Classifications

The American Physical Society has a revealed a new physics subject classification (called "Physics Subject Headings" and "PhySH" as a shorthand), and "networks" is listed as a primary category in the top level of classification. The study of networks has come a long way in terms of how it's perceived! Networks is indeed physics.

(Tip of the cap to Sang Hoon Lee.)

Jenga Experiment in Physical Review Letters

Take a look at this paper about Jenga in Physical Review Letters. OK, it's not literally about Jenga, but there is a figure in the paper that makes me think of Jenga, and the authors are discussing drilling holes to collapse a wooden cube. The paper is called "Critical Fragmentation Properties of Random Drilling: How Many Holes Need to Be Drilled to Collapse a Wooden Cube?"

This Random Walk is Not One of the Usual Suspects

The random walk in the paper "The Spacey Random Walk: a Stochastic Process for Higher-order Data" is not one of the usual suspects.

What Happens in Newcastle Stays in Newcastle (2016 Edition)

I just got back from spending a couple days in Newcastle with friends. And now back to "reality" in Oxford.

Base 11

Clearly we should be using base 11.

Which Equation is the Most Beautiful?

They survey N mathematicians and physicists, and asked them to state which equation they think is the most beautiful.

Survey says?

(P.S. I wish this were a real question on Family Feud.)

News Flash: "Former White Sox Prospect Breaks into Pittsburgh Office, Eats Pizza, Falls Asleep"

Um, OK.

According to the CEO of the company whose office the prospect broke into, "The fridge was filled with leftover pizza, and he came in and just dumped a whole bunch of stuff out, dumped pizza out, and there’s trails of pizza leading to the backroom.”

It's too bad that he's a human and not a ninja turtle.

Congratulations to Dr. Marya Bazzi and Dr. Lucas Jeub!

I can now officially congratulate my doctoral students Dr. Marya Bazzi and Dr. Lucas Jeub, who passed their thesis defenses last month and who received 'leave to supplicate' yesterday. It is the latter bureaucratic condition that implies that everything is now done.

Both Marya (who is jointly supervised with Sam Howison) and Lucas work on problems in community detection. Marya has developed methods for the study of multilayer community detection, especially in multilayer representations of temporal networks. Her first paper, which is a methods paper but uses data from finance to help illustrate her findings, just came out in final form. Lucas's first paper, on a local method for community detection, was published early last year. His second paper, which applies these ideas to multilayer networks, is on the arXiv. In his thesis, Lucas also studied hair-product data from Unilever.

Lucas and Marya are finishing up follow-up work, including a paper that they are coauthoring. Stay tuned.

"Heterogeneous, Weakly Coupled Map Lattices"

A new paper of mine just came out in final form today (though the typesetters were supposed to send us another set of page proofs, and sure enough issues that we pointed out with references leading to dead links in the references still have not been fixed completely). In any event, while we attempt to get them to correct their mistakes, here are some details about the article.

Title: Heterogeneous, Weakly Coupled Map Lattices

Authors: Ma Dolores Sotelo Herrera, Jesús San Martín, and Mason A. Porter

Abstract: Coupled map lattices (CMLs) are often used to study emergent phenomena in nature. It is typically assumed (unrealistically) that each component is described by the same map, and it is important to relax this assumption. In this paper, we characterize periodic orbits and the laminar regime of type-I intermittency in heterogeneous weakly coupled map lattices (HWCMLs). We show that the period of a cycle in an HWCML is preserved for arbitrarily small coupling strengths even when an associated uncoupled oscillator would experience a period-doubling cascade. Our results characterize periodic orbits both near and far from saddle–node bifurcations, and we thereby provide a key step for examining the bifurcation structure of heterogeneous CMLs.

"Mistakes Reviewers Make"

Here is a useful article about mistakes reviewers make and things to think about when one writes a referee report on a paper. It's good for both junior and senior people, and reminders even for senior people (myself very much included) is definitely a good thing. (It's views on how much one should stress the details versus the big picture of a paper do, however, appear to be different from mine. I didn't look at that part carefully but focused on the headline points rather than on the details therein --- possibly ironically.)

(Tip of the cap to Vinko Zlatić and Bruno Gonçalves.)

Flirting with Danger

I am flirting with danger with the two parts of my new portable harddrive.

My Coffee (and Chicory) Essence

It's my essence! Mine! Mine!

Naturally, it expels the old method as if it were a delinquent student.

(Tip of the cap to David Fallon.)

Oh, Britain –– For Shame

Really, Great Britain? For shame. (And for fuck's sake.)

I could go on a long rant, but I would only expend energy and fumes. I wish I could at least say that I am surprised, but I'm not. Foreigners are made to feel very unwelcome here (and both my students and I have experienced it often), and it was only a matter of time before something like this happened.

For shame.

Update (2/22/16): And here is another horror story. (Tip of the cap to Yves van Gennip.)

Quote of the Day: Hashtag Edition

Today's SMBC has a priceless quote: "There can be no quarter when facing the hoary countenance of evil. I must select my hashtag with care."

(The rest of today's comic strip is meh.)

The Acoustics of Breaking Chopsticks

In my latest post for the Improbable Research blog, I discuss the acoustics of breaking chopsticks.

Theorem: There Exist Arbitrarily Long Songs of Complexity O(1)

As discussed in a paper by Donald Knuth, the proof is due to Casey and the Sunshine Band.

Every Flavor Except for a Set of Measure Zero?

I saw these Harry-Potter-inspired jelly beans at a market many years ago, and I was struck by "Every Flavor Beans" now coming with two more flavors. Perhaps they mean every flavor except for a set of measure zero?

The Most Googled Job in Each State

Here is a visualization of some jobs that each U.S. state led in Google searches. Some of these are fantastic.

(Tip of the cap to Kin Chan.)

Website: "Sweatpants and Coffee"

I just encountered the website Sweatpants and Coffee from a link in Jennifer Nicoll Victor's Facebook post.

The only reason I am blogging about this is because the site's title is particularly apt for me.

Visualization: California for Beginners

This visualization provides a good summary of California for beginners.

(Tip of the cap to Maria King.)

RIP Animal (1950–2016)

With rock legend David Bowie and other prominent rockers (like Glenn Frey, who was a founding member of the Eagles, and several others) dying in their late 60s (or sometimes early 70s) the last couple of weeks, January 2016 really feels like "The Month the Music Died" (especially with rock music), this article about Animal dying at age 66 is a parody that somebody had to write.

For music, this has been a really awful month...

(Tip of the cap to Chris Howland.)

Ancient Egyptian d20

Apparently, Ancient Egyptians made small model icosohedrons (i.e., d20s, for those with a role-playing game bent).

One day, I hope that somebody unearths a character sheet, written in hieroglyphics, that was buried with an ancient Egyptian royal.

(Tip of the cap to Steven Wilson.)

Periodic Table Battleship!

I approve!

Freeway Knot Theory

Some help from knot theorists would be appreciated. Here is a photoshopped picture of a freeway (based on a real one in Oakland, California) that needs to be untangled.

(Tip of the cap to Stanley Somers.)

Note: The original version of my post described the picture incorrectly as being an actual freeway. See this link. Also, this freeway is knotted up even more severely. :)

Getting the Last Word

Sometimes, to get the last word, you have to put it on the epitaph of your tombstone.

I have seen a few of these before. Several of them are glorious.

(Tip of the cap to George Takei.)

Subtly Messing with People

I am highly amused by these 20 ways of subtly messing with people (though some of them are not very nice at all).

(Tip of the cap to George Takei.)

Nine Simples Rules for The Roadrunner and Wile E. Coyote

Here they are.

Despite one of the rules listed on that site, there was occasionally a bit of other dialog, especially on written signs.

(Tip of the cap to George Takei.)

Your Citizens Demand Whales

Then they shall have whales.

What Happens in Brussels Stays in Brussels

I am now off to Brussels for the final grant review meeting for the PLEXMATH consortium.

The Onion Does the BCS

Yes, yes it does. :)

"Community Detection in Temporal Multilayer Networks, with an Application to Correlation Networks"

One of my papers was just published in final form a few days ago. As the title indicates, this paper concerns community detection in temporal multilayer networks. Here are the title, authors, and abstract.

Title: Community Detection in Temporal Multilayer Networks, with an Application to Correlation Networks

Authors: Marya Bazzi, Mason A. Porter, Stacy Williams , Mark McDonald, Daniel J. Fenn, and Sam D. Howison

Abstract: Abstract. Networks are a convenient way to represent complex systems of interacting entities. Many networks contain “communities” of nodes that are more densely connected to each other than to nodes in the rest of the network. In this paper, we investigate the detection of communities in temporal networks represented as multilayer networks. As a focal example, we study time-dependent financial-asset correlation networks. We first argue that the use of the "modularity" quality function –– which is defined by comparing edge weights in an observed network to expected edge weights in a "null network" –– is application-dependent. We differentiate between "null networks" and "null models" in our discussion of modularity maximization, and we highlight that the same null network can correspond to different null models. We then investigate a multilayer modularity-maximization problem to identify communities in temporal networks. Our multilayer analysis depends only on the form of the maximization problem and not on the specific quality function that one chooses. We introduce a diagnostic to measure persistence of community structure in a multilayer network partition. We prove several results that describe how the multilayer maximization problem measures a trade-off between static community structure within layers and larger values of persistence across layers. We also discuss some computational issues that the popular "Louvain" heuristic faces with temporal multilayer networks and suggest ways to mitigate them.

RIP David Bowie (1947–2016)

Today, we lost a music legend: David Bowie has died of cancer. His last album was released three days ago (last Friday, on his 69th birthday).

There are numerous excellent David Bowie songs --- so much good (and very innovative) music! RIP.

Update: There is more detail in the BBC obituary. Here is the CNN obituary.

Update: As discussed in this article in The Telegraph, the timing of the release of David Bowie's final album last Friday was as a 'parting gift' to his fans. And the video for "Blackstar", which completes the saga both of Major Tom and of David Bowie, is chilling (especially in the context that it has turned out to have).

Update (1/12/16): Also look at these final pictures of David Bowie from last Friday. Amazing!

Update (1/12/16): I should have mentioned the following for those of you who don't already know: In addition to my really liking quite a lot of David Bowie's songs, Bowie exerted a major influence on so many of my favorite artists. The music to which I listen every day, and which gives me a great deal of pleasure, owes a Hell of a lot to David Bowie.

Update (1/13/16): Also see this small collection of tributes. Also don't forget this video (which was first posted in 2013, though is appropriate now more than ever).

Update (1/16/16): Here is visualization of many prominent musical artists and others who were influenced by David Bowie. (Tip of the cap to Duran Duran's post on Facebook.)

What Happens in Wroclaw Stays in Wroclaw (2016 Edition)

Tomorrow, I'll be flying to Network Science X 2016. I'll be giving one of the invited talks.

Apparently, there is going to be some free ice skating at the conference venue. This deserves a Mel-Brooksian "SEE NetSci on Ice!"

Also, this leads to the obvious hashtag ‪#‎NetSciOnIce‬ , which isn't cool yet but hopefully will be.

The Impressive Strength of Interleaved Phonebooks

My latest entry for the Improbable Research blog concerns the impressive strength of interleaved phonebooks.

I managed to miss the blog entry about this that appeared in August. Oops! But at least I coined the phrase "Hercules number".

Eastman–Kodak and the 13-Month Calendar

Yes, really. So cool!

(Tip of the cap to Karen Kustedjo.)

Update (1/23/16): I wrote about the 13-month calendar for the Improbable Research blog.

Choreographic Crystals!

Theorists have formulated a new kind of crystal that they have dubbed "choreographic crystals". Very cool!

Dodgers Signing of Pitcher Kenta Maeda is Now Official

The Dodgers have now officially signed pitcher Kenta Maeda to an 8-year deal.

(After counting two too many chickens with certain prior pitching "acquisitions", which both fell apart, I waited to post this blog entry until the deal with Maeda became official.)

Curative Properties of Chicken Soup?

This article --- and, especially, its opening picture --- makes me want to have some chicken soup.

(Tip of the cap to I Fucking Love Science.)

New Baseball Hall of Famers

Baseball's new Hall of Famers were announced last night: first-time candidate Ken Griffey Jr. was voted in with the highest percentage ever (99.3%, with 437 of 440 possible votes), and Mike Pizza was elected in his 4th year of eligibility.

Naturally, Piazza should have already been voted in 3 years ago, but such is life. (Other luminaries --- such as Carlton Fisk, Yogi Berra, and many others, also had to wait --- so it's not like that is new, though the back-acne McCarthyist steroid allegations are a different reason than in the past.) Jeff Bagwell, Tim Raines, Mike Mussina, and Curt Schilling made significant gains. Bagwell got over 70% of the vote and Raines got 69.8%, so I expect that they will both finally be elected next year. It's long past time. Trevor Hoffman also debuted on the ballot this year, and his 67.3% of the vote makes it very likely that he'll get elected in the next couple of years. (There is a good chance for next year, but I am not so sure.) Edgar Martinez made especially large gains, reaching a voting percentage of 43.4%, but he's running out of time. Then we have Roger Clemens and Barry Bonds...

Alan Trammell surpassed 40% of the vote in his last year on the ballot. It was also Mark McGwire's last year on the ballot. Unfortunately, Jim Edmonds didn't get the 5% of the vote needed to stay on the ballot next year; this is a shame, as he deserves a lot more consideration for the Hall than he got.

David Schoenfield discussed the winners and losers in this year's ballot.

Griffey is the first #1 overall draft pick to enter the Hall of Fame. By contrast, Piazza (1,390th pick, 62nd round, 1998) is the lowest ever draft pick to make the Hall. Griffey will presumably be enshrined as a Mariner, and Maybe Piazza will enter the Hall as a Marlin? ;) (I hope it will be the Dodgers, but I suspect it may well end up being the Mets.)

You can take a look at the Hall of Fame vote tracker to see many more details on the voting.

This page details newcomers who are eligible for the Hall of Fame ballot starting in 2017. Notable ballot debuts in 2017 include Vladimir Guerrero, Jorge Posada, Manny Ramirez, and Ivan Rodriguez. Of those, Rodriguez has the best chance of making it next year. No major new pitchers debut on the ballot until 2019, so that gives Mussina and Schilling a got chance to make additional major gains by then. Both of them are massively overqualified for the Hall of Fame.

Error Message in the Sky

Well, it's not quite a wheel in the sky, but this error message in the sky is awesome!

(Tip of the cap to Guillermo Valle Pérez.)

Ars Technica: "The Best New Board Games We Played in 2015"

Ars Technica has posted an article about their favorite new board games they played in 2015.

I am posting this for a specific reason: take a look at the designers of the game Roll for the Galaxy by Rio Grande Games! It's Caltech's very own Wei-Hwa Huang (from my era). Very cool!

(Tip of the cap to Nevin Liber.)

Dodgers Sign Free-Agent Pitcher

This time, it's for real: we have signed –– past tense! –– free agent pitcher Scott Kazmir to a three-year contract.

Awesome Embroidered Temari Spheres

These embroidered temari spheres are awesome!

(Tip of the cap to Association for Women in Mathematics.)

Awesome Visual Illusion

This visual illusion is really cool!

Note: I originally referred to this illusion as an "optical illusion", but my friend Steve Van Hooser, a visual neuroscientist, has pointed out my use of the incorrect term: "I know you are a stickler for details, and as a visual neuroscientist I feel you'd want to know: say "visual illusion" rather than "optical illusion". Because the visual system produces this illusion. There are true "optical" illusions, like the illusion of water on a hot road ahead. That is an optical illusion because it is the diffraction of light that causes the illusion." (I have made this same error on several prior blog posts, which I may eventually look up and correct.)

Today's Headline: "German Man Dies After Blowing Up Condom Machine"

I think we may have a winner in our Headline-of-the-Week competition: "German Man Dies After Blowing Up Condom Machine".

Yup, that's a pretty spectacular headline.

(Tip of the cap to Kin Chan.)

Life Imitates Fluxx

Following these parking instructions works just like in the game Fluxx, right?

Randomized Controlled Trials of Parachute Intervention

Apparently, there are none. At minimum, the paper called Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomised controlled trials reported the following summary of their results in the preamble to their paper: "We were unable to identify any randomised controlled trials of parachute intervention."

The paper does have a serious undertone, however, as the authors are commenting about the limits of evidence-based medicine.

(Tip of the cap to Easter Eggs in Scientific Papers.)

What Happens in the LA Basin Stays in the LA Basin

So to speak.

(Anyway, I'll be home for the holiday season.)

Amusing Animal Photos

These animal photos are very amusing.

Quantum Mosaic of John Stuart Bell

This mosaic of John Stuart Bell is very cool.

Tumblr: Math Professor Quotes

The Math Professor Quotes tumblr has just been brought to my attention.

(Tip of the cap to Association for Women in Mathematics.)

Would You Believe Zero Pitchers?

Just over a week ago, I thought we had signed one good pitcher and traded for another one, and now it seems that both deals have fallen through. Aroldis Chapman is being investigated under Major League Baseball's domestic-abuse policy, and the Dodgers found something they didn't like in Hisashi Iwakuma's physical. Our deal feel apart, and today comes the news that Iwakuma has resigned with the Mariners after all.

We've also lost Zack Greinke because we were unexpectedly stingy, so this hasn't been a particularly good offseason so far. Hopefully, the three-way trade with the Reds and White Sox will pave the way for acquiring somebody like José Fernández...

Comic Panels: "Good Mathematician vs Great Mathematician"

Here is a series of comic panels called "Good Mathematician vs Great Mathematician".

(Tip of the cap to Karen Kustedjo.)

"Complexity: A Story of Love and 'Power Laws'"

Apparently, somebody at Oxford is supposed to take complex systems and turn it into a work of fiction (taking inspiration from Alice in Wonderland, etc.)

"Complexity: A Story of Love and 'Power Laws'"@cgershen @SimonDeDeo @TahaYasseri

— Mason Porter (@masonporter) December 16, 2015

Ten Thousand Years of Fresh Air

Well, life once again imitates Spaceballs: A Canadian company is important canisters of clean air to China.

The need to get fresh air from the planet Druidia is one of the central plot points of Spaceballs. Here is one of the relevant quotes: Ah, planet Druidia. And under that air shield, ten thousand years of fresh air. We must get through that air shield!

And, of course, life has imitated Spaceballs several times: This includes not only an incident of "mowing the ocean" (which is only slightly more effective than combing the desert) and the hacking of a combination that is the kind of thing an idiot would have on his luggage but also a chastity belt and canned oxygen for sale. This story revisits the canned oxygen.

"I Don't Want to be a Pie!"

The Improbable Research Blog has passed along a pie chart that tabulates (or perhaps 'pie-bulates'?) the various causes of death in Shakespeare's plays. (Being baked into a pie would have to suck.)

Fractions of Worms and Singular Limits

Do you know what's worse than taking a bite out of an apple and finding a worm? Taking a bite of an apple and finding half a worm. And do you know what's even worse than that? Taking a bite and finding a quarter of a worm? And even worse than that is taking a bite and finding an eighth of a worm.

I can continue like this, and finding progressively smaller fractions of a worm after the delicious bite is progressively worse --- until we get to the situation in which we take a bite of an apple and don't have any worm. That's the best situation, as we have a normal delicious apple without any worm in it.* In mathematics, we refer to situations like this as a singular limit: the situation of setting a value equal to zero is qualitatively different from the situation of considering a sequence of values that we let approach zero. This is a very important concept in what is called singular perturbation theory, and it shows up all over the place in mathematics and its applications (e.g., in fluid mechanics, quantum mechanics and semiclassical limits, and many other places).

*Unless, of course, one swallows an entire worm with the bite, in which case it's a regular limit and we lose.

(Note: I don't remember seeing this analogy for singular limits before, but if somebody used it and I blocked out where I should be giving credit, please let me know. I could imagine somebody like Steve Strogatz using this type of analogy, for example, but I don't remember seeing him or anyone else use it.)

Update: Dominic Vella reminds me that Michael Berry used this analogy in an article in Physics Today. I definitely read that article, so I assume I got the analogy from there and forgot about it. I did have a nagging feeling that I must have seen it somewhere before even though I wasn't able to place it. And, no, I am not surprised that Michael Berry would use such an analogy. He's very good with analogies (and many other things).

Jose Canseco's Plans for Terraforming Mars

José Canseco has announced his plans for terraforming Mars on Twitter.

Clearly, this is a follow-up to his theory of gravity.

I love the terse 'trending' headline on Twitter.

Congratulations to Dr. Valentin Danchev!

The D.Phil. thesis of my student Valentin Danchev (now a postdoc in the Knowledge Lab at University of Chicago) has now been officially approved. Valentin's other supervisor was Michael Keith of COMPAS (Centre on Migration, Policy, and Society) at University of Oxford.

Valentin is a sociologist and was a D.Phil. student in University of Oxford's International Migration Institute. His thesis is called Spatial Network Structures of World Migration: Heterogeneity of Global and Local Connectivity, and we have a joint paper on the topic in progress. We plan to submit that paper to a sociology journal.

Functional MRI Measurements of People Eating High-Quality Versus Low-Quality Steaks

Yes, really.

New Dodger Pitchers (or Possibly Only One New Pitcher...)

The Los Angeles Dodgers have picked up two new pitchers: we signed free-agent starter Hisashi Iwakuma to a three-year deal, and we traded a pair of prospects to the Reds for power reliever Aroldis Chapman.

I hope we can pick up another good starter. Losing Zack Greinke to the Diamondbacks left a gaping hole in our rotation.

Update (12/08/15): Then again, it may take a few weeks for the trade for Chapman to go through --- if the Dodgers bother going through with the trade at all. (And is it really a good idea to acquire somebody with this kind of personal track record?)

Update (12/18/15): It may actually end up being zero pitchers. Um, bring back Zack Greinke?

Tales from the ArXiv: Modern Art

It is usually a good idea to preview the compiled file when you upload a paper to the arXiv. (The topic of the paper looks interesting, by the way.)

Otherwise, all of your figures might be plastered over each other on the same page.

"How Math Works": A Comic Strip About a Fundamental Truth

The new SMBC, which is titled "How Math Works", is spectacular. It also gets at a fundamental truth, and it does so in an amusing way. (It is of course exaggerated.)

Step 5: "I will never understand it. I will never believe it. As I go into death, with my final breath I spit on your theorem."

The other steps also speak the truth, and Step 4 is damn funny. Step 6 is also a familiar one.

Of course, pretty much all of science works this way. It is worth noting, however, that the notion of repeating experiments is a fundamental difference between science and pure mathematics.

The comic strip is of course exaggerated, but I do think it genuinely gets at a fundamental truth. Once a theorem is true, it is simply true; but if it changes a paradigm and people don't understand the argument, there can certainly be a lot of skepticism that can last a long time before things are accepted.

Update (12/14/15): Take a look at this post in the Improbable Research blog. It asks: "Does science really advance on funeral at a time?"

Front-Page Editorial in The New York Times

Today, The New York Times ran a front-page editorial for the first time since 1920. I'm very glad they've done this, and obviously it takes a lot for them to do this when the last one was almost 100 years ago. I hope it has an impact.

(Tip of the cap to Ernie Barreto and George Takei.)

What Research Papers Inspired Me?

I was asked to write about my favorite research papers (and why).

I answered what is perhaps a somewhat different question: What are some of the research papers that inspired me?

Here is my answer.

Math Postdoc Application Rage Thread

The title box of the math postdoc application rage thread on Reddit is all too real. My job applications were a long time ago, and I still have horrible memories of having to repeat the same damn piece of information on a form too many bloody times. In fact, I still have to do such damn things.

Design Fails

Here are some spectacular design fails.

(Tip of the cap to George Takei.)

Awesome Acknowledgements

The Science Easter Eggs blog illustrates a paper with a spectacular Acknowledgements section. (One of the authors also has the daycare that he currently attends listed as his affiliation.)

Tales from the ArXiv: Systemic Risk in a Galaxy Far, Far Away

Yes, really.

The abstract begins: In this paper we study the financial repercussions of the destruction of two fully armed andoperational moon-sized battle stations ("Death Stars") in a 4-year period and the dissolution ofthe galactic government in Star Wars.

(Tip of the cap to Guido Caldarelli.)

"Estimating Interevent Time Distributions from Finite Observation Periods in Communication Networks"

Here is the latest paper in my "please do this stuff more carefully" series.

People have been getting things wrong when it comes to examining inter-event time (IET) distributions, and there are methods from other fields (e.g., renewal processes) that allow one to correct for biases.

Here are the details of the paper.

Title: Estimating Interevent Time Distributions from Finite Observation Periods in Communication Networks

Authors: Mikko Kivelä and Mason A. Porter

Abstract: A diverse variety of processes––including recurrent disease episodes, neuron firing, and communication patterns among humans––can be described using interevent time (IET) distributions. Many such processes are ongoing, although event sequences are only available during a finite observation window. Because the observation time window is more likely to begin or end during long IETs than during short ones, the analysis of such data is susceptible to a bias induced by the finite observation period. In this paper, we illustrate how this length bias is born and how it can be corrected without assuming any particular shape for the IET distribution. To do this, we model event sequences using stationary renewal processes, and we formulate simple heuristics for determining the severity of the bias. To illustrate our results, we focus on the example of empirical communication networks, which are temporal networks that are constructed from communication events. The IET distributions of such systems guide efforts to build models of human behavior, and the variance of IETs is very important for estimating the spreading rate of information in networks of temporal interactions. We analyze several well-known data sets from the literature, and we find that the resulting bias can lead to systematic underestimates of the variance in the IET distributions and that correcting for the bias can lead to qualitatively different results for the tails of the IET distributions.

Tales from the ArXiv: Duck Dodgers and Bifurcation Diagrams

I hope that the authors of this paper make references to Duck Dodgers when they bring up this work in seminars.

Google + Star Wars

Yup, there is some cool stuff in the Google–Star Wars mash-up.

The Onion Win Again: U.S. Versus U.K. Edition

This new article from The Onion is funny (though also depressing because of how true it seems), and their tagline that compares the current health of the U.S. to the U.K. is positively hilarious: "Residents say that letting the U.S. pass peacefully is better than having to watch it linger on in agony like the United Kingdom."

Ranking Scientists According to Sarcasm

"Instead of using citations, I think we should rank scientists from most sarcastic to least."

Naturally, I was accused of using my own CV after I proposed that criterion for measuring quality.

Maybe I should call this metric the "p-index"? We could call it the "s-index", if you prefer, but then I wouldn't be naming it after myself.

The Physics of Chocolate Fountains

Here is a delicious exploration of the fluid mechanics of chocolate fountains.

(Tip of the cap to Aya Khaled Al-Zarka.)

2015 Dance Your Ph.D. Contest

You can see the winning videos in this article, which also includes a link to all 31 entries. (The overall winning entry includes some networks, and the winner in the physics category is from University of Oxford.) Very cool!

(Tip of the cap to Physics Today for this particular link. I saw a post earlier in the day from IFLS.)

RIP Carla Martin (1972–2015)

A bunch of us who went to school with Carla at the Center for Applied Mathematics at Cornell University have written an obituary for her. It appeared online yesterday in SIAM News. Go read it and see how she was an inspiration to students. (I would like not to need to work on another obituary like this for one of my friends for a very long time...) Also look at our coauthored paper on the singular value decomposition.

Carla died tragically last month.

Oxford's 2015 Mathematical Bake-Off

Pictures from the Mathematical Institute's 2015 mathematical bake-off are now posted!

The Menger sponge cake, which was the winning entry in the undergraduate-cake category, was created by two of our students (Louise O'Rourke and Sndrew Tweddle) in Somerville. Excellent job!

Don't Drink the Water (and Don't Breathe the Air)

Apparently, the news (rather ambiguously phrased, too) out of the Andrew Wiles Building is "Don't drink the water."

As the most recent e-mail indicates, "there may be a problem with the drinking water supply". And remember how the word "may" gets used in that context in the UK...

So, in honor of the situation, here is an appropriate song.

Tweeting Cats During the Brussels Lockdown

This is spectacular! Well played, Belgium. Very well played.

Dave Roberts is the New Dodger Manager

Dave Roberts is the new Dodger manager.

What Happens in San Francisco Stays in San Francisco

In a few hours, I'll be flying out to San Francisco to go to the wedding of one of my best friends. I'll only be there until Tuesday, so I'll also be wracking my body.

Amusing Book Dedications

The signal:noise on this list of book dedications is a bit suboptimal, but there are a few spectacular ones.

And mathematicians will very much appreciate the appearance of item #6.

(Tip of the cap to George Takei.)

Limit-Cycle-Oscillator Models of Bipolar Disorder: Revisited

Years ago, Steve Wirkus and I coauthored (with several undergraduate students) a paper that first introduced the idea of using limit-cycle oscillators to model bipolar patients. Our model was a toy model, but years later several of my colleagues at Oxford have been doing amazing things from a more data-centric perspective. Their latest paper is especially exciting for me. It does what we dreamed about and speculated about 12 years ago in our paper: taking the basic idea of a limit-cycle oscillator and combining it with clinical data in a realistic way. (The authors of this work understandably also incorporate noise into their model.)

Quoting the last few lines of our conclusions: "In this respect, we view our work as a first step in developing mathematical models of the mood swings of bipolar individuals. Our intent is to provide a mathematical framework that ultimately leads to the development of more detailed models of bipolar disorder that incorporate clinical data. With this work, we hope to motivate the collection of time-series data from clinical trials that will lead to refinements of our model that incorporate such data. In our view, dynamical systems theory and mathematical modeling in general can lead to important advancements in the understanding of bipolar disorder."

(Tip of the cap to Society for Industrial and Applied Mathematics, who shared a popular account of the work on Facebook.)

2016 Most Valuable Player Awards

The expected --- and correct --- players won the Most Valuable Player awards.

Bryce Harper of the Washington Nationals is the 2016 National League MVP. He won unanimously: he was named first on all 30 ballots, which gives him 420 total points. Paul Goldschmidt of the Arizona Diamondbacks finished second in the voting with 234 points, and Joey Votto of the Cincinnati Reds finished third with 175 points.

Josh Donaldson of the Toronto Blue Jays is the 2016 American League MVP. He garnered 23 first-place votes and 385 votes in total. Mike Trout of the Los Angeles Angles of Anaheim (aka "The The Angels Angels of Anaheim") finished second with 304 votes (he had the other 7 first-place votes). Lorenzo Cain of the Kansas City Royals finished third with 225 points.

This page shows the number of votes garnered by a few more players. (For example, Zack Greinke finished 7th in the voting in the NL.)

For the complete tabulation of the votes, see this website. (Clayton Kershaw finished 10th in the balloting.)

Twitter User @MrSnuffleupagus Follows Exactly One User: @BigBird

Twitter user @MrSnuffleupagus follows exactly one user: @BigBird.

Now that's a great new-school twist on something old-school!

(Tip of the cap to Gregory Fricke​ for the article that led me to the above factoid.)

Jake Arrieta and Dallas Keuchel Win 2016 Cy Young Awards

Baseball's Cy Young Awards were announced yesterday.

Jake Arrieta of the Chicago Cubs won in the National League, and Dallas Keuchel of the Houston Astros won in the American League.

Arrieta received 17 of the 30 first-place votes and 169 points in total. Zach Greinke of the Dodgers finished second with 147 points (with 10 first-place votes), and Clayton Kershaw of the Dodgers finished in third with 101 points (with 3 first-place votes). I figured that Arrieta would win, given the storyline and his dominance in the second half of the season, but I think Greinke deserved the award very slightly more than Arrieta.

Keuchel received 22 of 30 first-place votes and 186 points in total. David Price (of the Detroit Tigers and then Toronto Blue Jays) came in second with 143 points (with 8 first-place votes), and Sonny Gray of the Oakland Athletics finished third with 82 points.

The complete vote tallies are available on this page.

What Happens in Florence Stays in Florence

Late last night, I made it to Florence, Italy for the COSMOS workshop on complex oscillatory systems, where I was asked to give an introductory talk on networks and dynamics. The talk took place at the Galileo Galilei Institute for Theoretical Physics. (Perhaps it is the queen of theoretical-physics institutes? At minimum, I am sure it is mercurial.)

My hotel is located on Viale Machiavelli, and the GGI is located on Largo Enrico Fermi.

2016 Managers of the Years

Major League Baseball's Manager of the Year awards were announced last night. Joe Madden of the Chicago Cubs won the award in the National League, and Jeff Banister of the Texas Rangers won the award in the American League.

Kris Bryant and Corlos Correa are the 2016 Baseball Rookies of the Year

Kris Bryant of the Chicago Cubs and Carlos Correa of the Houston Astros have won the 2016 Rookie of the Year awards.

Unsurprisingly, Bryant was the unanimous winner in the National League, as he was named in the first slot on all 30 NL ballots. Matt Duffy of the San Francisco Giants was the runner-up in the National League, and Jung Ho Kang of the Pittsburgh Pirates finished in third place.

Carlos Correa was named first on 17 of the 30 American League ballots to become the AL Rookie of the Year. Correa had 124 total points. Francisco Lindor, with 13 first-place votes and 109 total points, was the runner-up. Miguel Sano finished in third place.

A Universal Law of Happiness

The statistical physicists need to get cracking on this one.

Neuroimaging Study of Neuroscientists' Reactions to Journal Impact Factors

Well, we seem to be getting a bit meta here...

A group of scientists has conducted a neuroimaging study of neuroscientists' reactions to journal impact factors.

Here is a short excerpt from the body of the paper: "Using functional magnetic resonance imaging, we examined the brain activity of N = 18 neuroscientists during the anticipation of their own publication."

And here is the paper's abstract:

The incentive structure of a scientist’s life is increasingly mimicking economic principles. While intensely criticized, the journal impact factor (JIF) has taken a role as the new currency for scientists. Successful goal-directed behavior in academia thus requires knowledge about the JIF. Using functional neuroimaging we examined how the JIF, as a powerful incentive in academia, has shaped the behavior of scientists and the reward signal in the striatum. We demonstrate that the reward signal in the nucleus accumbens increases with higher JIF during the anticipation of a publication and found a positive correlation with the personal publication record (pJIF) supporting the notion that scientists have incorporated the predominant reward principle of the scientific community in their reward system. The implications of this behavioral adaptation within the ecological niche of the scientist’s habitat remain unknown, but may also have effects which were not intended by the community.