"Adapting InfoMap to Absorbing Random Walks Using Absorption-Scaled Graphs"

One of my papers just came out in final published form. Here are some details.

Title: Adapting InfoMap to Absorbing Random Walks Using Absorption-Scaled Graphs

Authors: Esteban Vargas Bernal, Mason A. Porter, and Joseph H. Tien

Abstract: InfoMap is a popular approach to detect densely connected "communities" of nodes in networks. To detect such communities, InfoMap uses random walks and ideas from information theory. Motivated by the dynamics of disease spread on networks, whose nodes can have heterogeneous disease-removal rates, we adapt InfoMap to absorbing random walks. To do this, we use absorption-scaled graphs (in which edge weights are scaled according to absorption rates) and Markov time sweeping. One of our adaptations of InfoMap converges to the standard version of InfoMap in the limit in which the node-absorption rates approach 0. We demonstrate that the community structure that one obtains using our adaptations of InfoMap can differ markedly from the community structure that one detects using methods that do not account for node-absorption rates. We also illustrate that the community structure that is induced by heterogeneous absorption rates can have important implications for susceptible–infected–recovered (SIR) dynamics on ring-lattice networks. For example, in some situations, the outbreak duration is maximized when a moderate number of nodes have large node-absorption rates.

Shohei Ohtani Joins the 50/50 Club (and Has One of the Best Single-Game Performances in Baseball History)

Shoehei Ohtani makes a habit of doing things that none of us have ever seen before.

During today's game, he became the inaugural member of the "50/50 Club", as he now has both 50+ home runs and 50+ stolen bases this year. No member of the 50-home-run club had ever stolen even as many as 30 bases before.

He also joined the club in spectular fashion today with a game for the ages. Ohtani's performance today was one of the best single-game performances in Major League Baseball history. He went 6 for 6 with 2 doubles, 3 home runs, 10 runs batted in, 4 runs, and 2 stolen bases. There have been only 16 games in Baseball history in which a player has 10+ RBIs; this is the first one by a Dodger. This is the first time in Baseball history that a player has had 3+ home runs and 2+ stolen bases in the same game.

Since the RBI became an official statistic in 1920, Shohei Ohtani is now the only player in Baseball history who has a game — any game, so they each can occur in different games — in their career with 10+ RBIs, 6+ hits, 5+ extra-base hits, 3+ HRs, and 2+ SBs. Any game. Ohtani did them all in the same game. Amazing!

I have never seen any game like this in my life before.

(P.S. The Dodgers clinched a playoff berth with their victory today.)

2024 Ig Nobel Prizes

The 2024 Ig Nobel Prizes were awarded in a ceremony this evening.

There are so many great ones this year that it's hard to pick my favorites.

What Happens in Ann Arbor Stays in Ann Arbor

I am off to Ann Arbor, Michigan. I'll be visiting University of Michigan to give a colloquium in their Department of Computational Medicine & Bioinformatics.

What Happens in Los Alamos Stays in Los Alamos

I am heading over to Los Alamos for a networks workshop.

That's right. I'll be spending a few days in the wild, wild West.

"Persistent Homology for Resource Coverage: A Case Study of Access to Polling Sites"

One of my paper was published in final form last week. Here are some details.

Title: Persistent Homology for Resource Coverage: A Case Study of Access to Polling Sites

Authors: Abigail Hickok, Benjamin Jarman, Michael Johnson, Jiajie Luo, and Mason A. Porter

Abstract: It is important to choose the geographical distributions of public resources in a fair and equitable manner. However, it is complicated to quantify the equity of such a distribution; important factors include distances to resource sites, availability of transportation, and ease of travel. We use persistent homology, which is a tool from topological data analysis, to study the availability and coverage of polling sites. The information from persistent homology allows us to infer holes in a distribution of polling sites. We analyze and compare the coverage of polling sites in Los Angeles County and five cities (Atlanta, Chicago, Jacksonville, New York City, and Salt Lake City), and we conclude that computation of persistent homology appears to be a reasonable approach to analyzing resource coverage.

What Happens in Glasgow Stays in Glasgow

I am off to Glasgow for the 2024 World Science-Fiction Convention (i.e., WorldCon). I am involved in a talk and some panels.

What Happens in Frankfurt Stays in Frankfurt

I am going to be in Frankfurt for a few days for a workshop on metric networks that I coorganized.

What Happens in Oxford Stays in Oxford

I am off to Oxford to spend most of the next few weeks. I'll also have a short embedded trip to Frankfurt and will be heading to Glasgow after my time in Oxford.

RIP Barry Wellman (1942–2024)

I'm very sad to hear about sociologist Barry Wellman's death.

He was one of the people who welcomed me warmly to the Sunbelt community (though he did make a point to inform me, with much spittle flying in the process, of course, that the Dodgers shouldn't have left Brooklyn).

I figured (but never officially knew) that Barry had been sick for a while, given his sudden lack of activity starting a couple of years ago on Facebook and SOCnet after always making a point of stressing that the point of such social gathering spaces (including social media) was to be very active, so he always purposely did that.

(h/t through the SOCnet mailing list)

RIP Martin Mull (1943–2024)

Comedic actor, musician, and painter Martin Mull dies yesterday.

I found out about him via the song "Dueling Tubas", which I first learned about in Physics 2a through an acoustics demo by now-Nobel Laureate David Politzer.

My musically-inclined classmates were in emotional pain.

RIP Willie Mays (1931–2024)

The legendary Willie Mays died today. Mays was the oldest living baseball Hall of Famer; he took the mantle in 2021 when Tommy Lasorda died. You can see Willie Mays' statistics on this page.

I believe that Luis Aparicio is now the oldest living baseball Hall of Famer.

"Emergence of Polarization in a Sigmoidal Bounded-Confidence Model of Opinion Dynamics"

A paper of mine was just published in final form. Here are zome details.

Title: Emergence of Polarization in a Sigmoidal Bounded-Confidence Model of Opinion Dynamics

Authors: Heather Z. Brooks, Philip S. Chodrow, and Mason A. Porter

Abstract: We study a nonlinear bounded-confidence model (BCM) of continuous-time opinion dynamics on networks with both persuadable individuals and zealots. The model is parameterized by a nonnegative scalar \gamma, which controls the steepness of a smooth influence function. This influence function encodes the relative weights that individuals place on the opinions of other individuals. When \gamma = 0, this influence function recovers Taylor's averaging model; when \gamma \rightarrow \infty, the influence function converges to that of a modified Hegselmann--Krause (HK) BCM. Unlike the classical HK model, however, our sigmoidal bounded-confidence model (SBCM) is smooth for any finite \gamma. We show that the set of steady states of our SBCM is qualitatively similar to that of the Taylor model when \gamma is small and that the set of steady states approaches a subset of the set of steady states of a modified HK model as \gamma \rightarrow \infty. For certain special graph topologies, we give analytical descriptions of important features of the space of steady states. A notable result is a closed-form relationship between graph topology and the stability of polarized states in a simple special case that models echo chambers in social networks. Because the influence function of our BCM is smooth, we are able to study it with linear stability analysis, which is difficult to employ with the usual discontinuous influence functions in BCMs.

What Happens in Warsaw Stays in Warsaw

I am heading to Warsaw to participate a couple of days in the WAW 2024 conference. This is my first trip to Poland in several years, and unfortunately it's going to be very brief.

"Inference of Interaction Kernels in Mean-Field Models of Opinion Dynamics"

A paper of mine just came out in final form. Here are some details about it.

Title: Inference of Interaction Kernels in Mean-Field Models of Opinion Dynamics

Authors: Weiqi Chu, Qin Li, and Mason A. Porter

Abstract: In models of opinion dynamics, many parameters — either in the form of constants or in the form of functions — play a critical role in describing, calibrating, and forecasting how opinions change with time. When examining a model of opinion dynamics, it is beneficial to infer its parameters using empirical data. In this paper, we study an example of such an inference problem. We consider a mean-field bounded-confidence model with an unknown interaction kernel between individuals. This interaction kernel encodes how individuals with different opinions interact and affect each other's opinions. Because it is often difficult to quantitatively measure opinions as empirical data from observations or experiments, we assume that the available data takes the form of partial observations of a cumulative distribution function of opinions. We prove that certain measurements guarantee a precise and unique inference of the interaction kernel and propose a numerical method to reconstruct an interaction kernel from a limited number of data points. Our numerical results suggest that the error of the inferred interaction kernel decays exponentially as we strategically enlarge the data set.

Shōgun (2024)

I just finished watching the 2024 Shōgun, which I enjoyed very much.

I read the book around December 1988 — followed over the next years of reading every single other Asia-saga novel that James Clavell wrote — during my elementary school's winter break. I was so captivated that that was basically all I did during that winter break. I was already a slow reader back then, and now I read much more slowly than I did back then. (I also don't have time to basically only read a book nonstop for a couple of weeks.) I was fascinated by the epic combined with the portrayal of how East and West saw each other through their interactions. This was the first book in my life that had ever captivated me that way, and I was really excited when I saw a poster for the new miniseries a few months ago.

The 2024 series did a great job of capturing that, and it was aspects of those interactions and contrasting views (and part of the scene of peeing in a garden to consummate an agreement, and I am pretty sure that I know which scene in the new tv series corresponds to that vignette) that really stood out to me. However, most of this runs together through all of Clavell's works, and I can't really separate Shōgun from the others. I had forgotten almost all of the plot, but from Wikipedia it seems that the new series adapted it very well.

I never watched the 1980 miniseries. There was a 1988 miniseries of Nobel House. I also never watched that one, but I did notice Shōgun and Tai-Pan (and knew that Nobel House was by the same author, and Tai-Pan also caught my eye because of the Apple II game of almost the same name that was inspired by the novel) on a bookshelf in my parents' house (nobody else in the household had read these epic books), so I picked up Shōgun, which became an important part of my own personal history, even though I forgot so much of it.

I suppose that a new Nobel House miniseries may be possible? That one, too, was a particularly awesome book. (I also enjoyed the others, although I gave up on Tai-Pan the first time and started over and read it only a couple of years after, because I could put up with the rougher writing of that earlier work with the thoughts of it as a prequel to Nobel House.)

What Happens in San Francisco Stays in San Francisco (again)

I am heading to San Francisco for a cousin's wedding.

RIP David Goodstein (1939–2024)

David Goodstein (an emeritus physics professor at Caltech) died yesterday. This is the end of an era.

I watched many of The Mechanical Universe videos in high school. The beginning and end of each video showed Goodstein lecturing to students in the big Caltech physics lecture hall. I had Goodstein for Physics 1a (mechanics) in fall of my frosh year in that same lecture hall, and I remember how surreal it felt. That was one of my big "Wow, I am now at Caltech." things. Also, I came out of lectures feeling that I understood the material — but then I tried the homework and saw that I didn't actually yet understand it.

(h/t Barry Simon)

What Happens in Hanover Stays in Hanover

I am heading to New Hampshire for the first time ever. I'll be in Hanover to give the mathematics colloquium at Dartmouth College.

What Happens in New York City Stays in New York City

I'm heading off to New York City for the first time in many years. I'll be giving a talk at The Rockefeller University.