Wednesday, March 29, 2017

The Quotable Mark Twain

As I am in Missouri for the first time, I think it's appropriate that I offer up some quotes from Mark Twain, a purveyor of snark from days gone by.

Here's a nice (and topical) one to start us off: "Get your facts first, and then you can distort them as much as you please."

Fake News from Moose & Squirrel

This cartoon from The New Yorker also alludes to the characters Boris and Natasha. They were the adversaries in The Rocky and Bullwinkle Show.

I recently saw this awesome license plate that does so as well.

I really enjoy alluding to the characters Boris and Natasha. I did that recently in my winning entry in a caption content, and I did it in 2006 in an Aprils Fool's Day prank.

What Happens in St. Louis Stays in St. Louis

I am heading off to St. Louis to give a talk in the physics department at Washington University (WUSTL).

This is my first ever trip to Missouri.

A little while ago, after I went through the x-ray machine, the TSA agents wanted to check my hair to make sure I wasn't hiding something in there. (This happens a couple of times every year.)

Monday, March 27, 2017

A Random Walk Through Public Broadcasting

A few days ago, PBS posted a video introducing random walks to a public audience! Sweet!

Update: This is an episode of a mathematics show called "Infinite Series". The above episode refers to an episode about Markov chains. Take a look at their YouTube channel and Twitter feed.

Saturday, March 25, 2017

"Eigenvector-Based Centrality Measures for Temporal Networks"

One of my papers came out in final published form yesterday. Here are the details.

Title: Eigenvector-Based Centrality Measures for Temporal Networks

Authors: Dane Taylor, Sean A. Myers, Aaron Clauset, Mason A. Porter, and Peter J. Mucha

Abstract: Numerous centrality measures have been developed to quantify the importances of nodes in time-independent networks, and many of them can be expressed as the leading eigenvector of some matrix. With the increasing availability of network data that changes in time, it is important to extend such eigenvector-based centrality measures to time-dependent networks. In this paper, we introduce a principled generalization of network centrality measures that is valid for any eigenvector-based centrality. We consider a temporal network with N nodes as a sequence of T layers that describe the network during diff erent time windows, and we couple centrality matrices for the layers into a supracentrality matrix of size NT x NT whose dominant eigenvector gives the centrality of each node i at each time t. We refer to this eigenvector and its components as a joint centrality, as it reflects the importances of both the node i and the time layer t. We also introduce the concepts of marginal and conditional centralities, which facilitate the study of centrality trajectories over time. We find that the strength of coupling between layers is important for determining multiscale properties of centrality, such as localization phenomena and the time scale of centrality changes. In the strong-coupling regime, we derive expressions for time-averaged centralities, which are given by the zeroth-order terms of a singular perturbation expansion. We also study first-order terms to obtain fi rst-order-mover scores, which concisely describe the magnitude of the nodes' centrality changes over time. As examples, we apply our method to three empirical temporal networks: the United States Ph.D. exchange in mathematics, costarring relationships among top-billed actors during the Golden Age of Hollywood, and citations of decisions from the United States Supreme Court.

Fermat's View of Twitter

In retrospect, I should have written "this tweet" instead of "a Twitter post" to make the parallel even stronger.

Thursday, March 23, 2017

GOP: Dungeons and Dragons Edition

The D & D themed trolling of the Republicans is hilarious. I am highly amused.

(Tip of the cap to Rachael Rosenthal.)

Update (3/27/17): This article in The Washington Post includes several more spectacular examples of GOP D & D. By the way, the hashtag is #GOPDnD. (Tip of the cap to Mohi Kumar for this article.)

"The Multilayer Nature of Ecological Networks"

Our perspective paper on multilayer networks in ecology is out in final form today! Here are the details.

Title: The Multilayer Nature of Ecological Networks

Authors: Shai Pilosof, Mason A. Porter, Mercedes Pascual, and Sonia Kéfi

Abstract: Although networks provide a powerful approach to study a large variety of ecological systems, their formulation does not typically account for multiple interaction types, interactions that vary in space and time, and interconnected systems such as networks of networks. The emergent field of ‘multilayer networks’ provides a natural framework for extending analyses of ecological systems to include such multiple layers of complexity, as it specifically allows one to differentiate and model 'intralayer' and 'interlayer' connectivity. The framework provides a set of concepts and tools that can be adapted and applied to ecology, facilitating research on high-dimensional, heterogeneous systems in nature. Here, we formally define ecological multilayer networks based on a review of previous, related approaches; illustrate their application and potential with analyses of existing data; and discuss limitations, challenges, and future applications. The integration of multilayer network theory into ecology offers largely untapped potential to investigate ecological complexity and provide new theoretical and empirical insights into the architecture and dynamics of ecological systems.

Wednesday, March 22, 2017

An Evans Function: A Wronskian on Crack

Definition: An Evans function is a Wronskian on crack.

I'm pretty sure that this is the official definition that you'll find in many mathematics books.

In case you're interested in these objects, see Todd Kapitula's primer. And here is a new article by Chris Jones that reminded me of the above definition.

Actually, I'm pretty sure I once heard someone — maybe even Chris? — joking call an Evans function "a Wronskian on steroids" during a seminar. I remember thinking that 'on steroids' probably wasn't doing justice to the function.

An "Unsung" Collection of Songs

I love how words evolve: a collection of things that literally are sung are now "unsung" masterpieces, and it makes perfect sense.

Oh, what the bards of yore have wrought.

Tuesday, March 21, 2017

Yves Meyer Wins 2017 Abel Prize!

Yves Meyer has won the 2017 Abel Prize for his work on the theory of wavelets. Here is an article in Nature about it.

I am puzzled as to why Ingrid Daubechies didn't share this prize.

Update: Terry Tao has written a short blog post about the prize. Among other things (and I hadn't caught this), note the following text from Tao: Daubechies also made extremely important contributions to the theory of wavelets, but my understanding is that due to a conflict of interest arising from Daubechies’ presidency of the International Mathematical Union (which nominates members of the Abel prize committee) from 2011 to 2014, she was not eligible for the prize this year, and so I do not think this prize should be necessarily construed as a judgement on the relative contributions of Meyer and Daubechies to this field.

Wednesday, March 15, 2017

Oxford Comma: The Revenge

And, sometimes, the lack of an Oxford comma might determine the outcome of a court case.

Also see previous blog entries of mine, such as this one, this one, and this one.

Vindication is mine!

(Tip of the cap to Jaideep Taggart Singh.)

Update: Aaron Clements pointed me to this Washington Post article.

The Tensor: A Reboot of The Matrix

I assume that the reboot of The Matrix will be called "The Tensor".

Also see my Facebook post about this for witty repartee, other suggested names, and possible prequels (e.g., "The Vector").

(Tip of the cap to Sammy Kline for the information about the reboot.)

We Studied Network Structure, and Then the Murders Began

This article on The Daily Dot suggests adding the phrase "and then the murders began" to the first sentence of the book that one is reading. This can change the tone of the book in very amusing ways.

As a twist on this, I decided to look at the first sentence of the preface of one of my books. This yields the following sentence: "Traditionally, much of the study of networks has focused on structural features, and then the murders began."

Unfortunately, the tense of the sentence hurts things, so I am going to change one letter ("s" to "d" in the word "has") to produce the following sentence: "Traditionally, much of the study of networks had focused on structural features, and then the murders began."

Much better! (And highly amusing.)

(Tip of the cap to Keith Fraser.)

"Best-Tasting Colors"

I don't completely agree with the new XKCD, but there is some truth here.

I would move "cherry" way over to the right.

I did recently have an experience with eating a pink Starburst and expecting strawberry but getting watermelon instead. It was unpleasant.

Even more unpleasant are past experiences of eating red with the hope that it's cherry but then getting cinnamon instead.


Tuesday, March 14, 2017

Happy Pi Day!

Today is, of course, Pi Day. And I love how the Colorado Rockies celebrated it today!

(Tip of the cap to Jeremy Stell.)

Update (3/19/17): I forgot to mention that I found out a few days ago that there was some Photoshopping in the above picture. It's still very cool, though not quite as cool as before.

Sonyalytic Acquired by Spotify

OK, but what does that have to do with me?

Well, Martin Gould is CEO of Sonalytic, which was just acquired by Spotify! Very well done!

Saturday, March 11, 2017

"Artistic Expressions of Math Over Seven Centuries"

My favorite picture in this article (in Hyperallergic) by Allison Meier is "Garden of Mathematical Sciences". So sweet!

This article, which has lots of great pictures of mathematical art, is a review of the exhibit Picturing Math at the Metropolitan Museum of Art in New York City.

(Tip of the cap to James Tanton.)

Thursday, March 09, 2017

What Happens in Houston Stays in Houston

Today I am flying out to Houston to give the mathematics colloquium tomorrow at University of Houston, Downtown.

Wednesday, March 08, 2017

Reminder: You Should be Reading the @RoguePOTUSStaff Twitter Feed

Just as a reminder, you should definitely be reading the @RoguePOTUSStaff Twitter feed, which appears to be legit. It is also hilarious and gives fascinating insights as to what is going on in The White House days. For example, consider the following gem from today:

Wow. Amazing.

Here is an older blog entry about the rogue government Twitter accounts.

Tuesday, March 07, 2017

'E' is for Erdmann

Entry 'E' in the A-to-Z series on women mathematicians in the Life Through a Mathematician's Eyes tumblr is my Somerville College colleague Karin Erdmann.

It should say "specializes" (present tense), by the way, as Karin is still research-active, even though she's retired. In fact, no doubt, she is now more active in her research, as that is how it often works.

As I write this, the tumblr has gotten up to 'M' so far, and there are many great mathematicians profiled (including, thankfully, people besides the same ones that often show up over and over again in such lists).

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

Monday, March 06, 2017

The World in Miniature

The World in Miniature is an amazing collection of art that puts a really nice perspective on ordinary real-world object. So cool!

(Tip of the cap to Yves van Gennip.)

Sunday, March 05, 2017

Putin's Daughters and Oxford Commas

This tweet gives me a convenient opportunity to remind you of the importance of Oxford commas. I like the alternative interpretation, though!

Saturday, March 04, 2017

A Hierarchy of Types of Disagreement

I really like this pyramidal visualization of types of disagreement!

Thursday, March 02, 2017

Grilling a Lawmaker About his Degrees

Once again, truth is stranger than fiction. Check out this story.

In his tweet, Carl Bergstrom links to a Boing Boing article, but the article to which it links gives a clearer explanation.

It's not quite as surreal as a National Park Service Twitter account going rogue (initially by simply tweeting basic facts about climate science), but it's still odd.

RIP Eugene Garfield (1925–2017)

Eugene Garfield, one of the founders of bibliometrics and scientometrics, died a few days ago.

Garfield contributed a lot to the study of scientific productivity and output, and for better or for worse (often for worse), he gave us the impact factor (which of course has led to many variants).

Wednesday, March 01, 2017

Science has no Borders

As demonstrated at my undergraduate alma mater Caltech today, science has no borders.