16 hours ago

## Monday, February 29, 2016

## Saturday, February 27, 2016

### What Happens in Marina del Rey Stays in Marina del Rey

I am off to Marina del Rey for a wedding!

It's always nice on my body to go to California for the weekend and then return.

It's always nice on my body to go to California for the weekend and then return.

Labels:
California,
friends,
Southern California,
travel,
weddings

## Friday, February 19, 2016

### "Lost in Transportation: Information Measures and Cognitive Limits in Multilayer Navigation"

A new article of mine just came out in final form today in

*Science Advances*. Here are the details.**Title:**Lost in Transportation: Information Measures and Cognitive Limits in Multilayer Navigation**Authors:**Riccardo Gallotti, Mason A. Porter, and Marc Barthelemy**Abstract:**Cities and their transportation systems become increasingly complex and multimodal as they grow, and it is natural to wonder whether it is possible to quantitatively characterize our difficulty navigating in them and whether such navigation exceeds our cognitive limits. A transition between different search strategies for navigating in metropolitan maps has been observed for large, complex metropolitan networks. This evidence suggests the existence of a limit associated with cognitive overload and caused by a large amount of information that needs to be processed. In this light, we analyzed the world’s 15 largest metropolitan networks and estimated the information limit for determining a trip in a transportation system to be on the order of 8 bits. Similar to the "Dunbar number," which represents a limit to the size of an individual’s friendship circle, our cognitive limit suggests that maps should not consist of more than 250 connection points to be easily readable. We also show that including connections with other transportation modes dramatically increases the information needed to navigate in multilayer transportation networks. In large cities such as New York, Paris, and Tokyo, more than 80% of the trips are above the 8-bit limit. Multimodal transportation systems in large cities have thus already exceeded human cognitive limits and, consequently, the traditional view of navigation in cities has to be revised substantially.
Labels:
articles,
me,
multilayer networks,
networks,
physics,
publications,
transportation

## Wednesday, February 17, 2016

### Comparing Novels Based Only on Punctuation

Can one algorithmically discern writing styles in novels based only on punctuation (no words)?

Take a look at this discussion.

I want to see someone compare the writing styles of different scientists in this way. :)

(Tip of the hat to Santa Fe Institute.)

Take a look at this discussion.

I want to see someone compare the writing styles of different scientists in this way. :)

(Tip of the hat to Santa Fe Institute.)

**Update (3/19/16):**Here is my article on this for the Improbable Research blog.
Labels:
awesome,
complex systems,
data analytics,
grammar,
novels,
punctuation,
words

## Tuesday, February 16, 2016

### RIP Sir Christopher Zeeman (1925–2016)

Mathematician Sir Christopher Zeeman, a pioneer in dynamical systems (e.g., he is very famous for his work on catastrophe theory), died this weekend.

(Tip of the cap to Gail Cardew.)

(Tip of the cap to Gail Cardew.)

Labels:
dynamical systems,
mathematicians,
mathematics,
obituaries

## Monday, February 15, 2016

### A Temperature Scale with a Negative Slope

Yes, really. The Delisle (°D) temperature scale has a negative slope. (The original version of the Celsius scale did as well.) Check out Wikipedia's comparison of temperature scales.

I just tweeted about it.

I started going down the rabbit hole earlier today because of today's XKCD.

I just tweeted about it.

Delisle (°D): because we like temperature scales with a negative slope (cue Tom Jones): https://t.co/znCcYoJR0s pic.twitter.com/m5M5nmnyZa

— Mason Porter (@masonporter) February 15, 2016

I started going down the rabbit hole earlier today because of today's XKCD.

### Quantum Chess

I am a bit late to the game in watching the video of Quantum Chess. Go and watch it!

(It is excellent! Not bogus.)

(It is excellent! Not bogus.)

## Saturday, February 13, 2016

### 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.)

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.)

Labels:
arcade games,
awesome,
games,
museums,
video games

## Friday, February 12, 2016

### "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.

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.

Labels:
complex systems,
granular media,
me,
nonlinear waves,
physics,
publications,
research

## Thursday, February 11, 2016

### 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.

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.

Labels:
awesome,
Caltech,
comics,
discoveries,
physics

### Valentine's Day and Taking Limits

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

Labels:
amusing,
comics,
holidays,
limits,
mathematics

### 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.

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.

## Wednesday, February 10, 2016

### Instant Thesis Topic for Philosophy

Just follow the tip in today's SMBC.

Labels:
amusing,
comics,
dissertations,
philosophy,
snark

### 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.)

(Tip of the cap to Alice Prochaska.)

Labels:
awesome,
mathematicians,
money,
Somerville

### 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.)

(Tip of the cap to Sang Hoon Lee.)

Labels:
awesome,
classification,
networks,
ontologies,
physics

## Monday, February 08, 2016

###
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?"
Labels:
complex systems,
games,
percolation,
physics,
publications

### 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.

Labels:
actors,
articles,
arxiv,
mathematics,
movies,
networks,
puns,
random walks

## Sunday, February 07, 2016

### 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.

## Friday, February 05, 2016

### 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

Survey says?

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

*Family Feud*.)
Labels:
equations,
mathematicians,
mathematics,
physicists,
physics,
surveys

## Wednesday, February 03, 2016

### 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.

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.

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.

## Tuesday, February 02, 2016

### "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.
Labels:
dynamical systems,
mathematics,
me,
papers,
publications,
research

### "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.)

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

Labels:
publishing,
referee reports,
refereeing,
science

## Monday, February 01, 2016

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