Sam Zhang's Homepage

**I am a 5th year PhD candidate in applied mathematics** at the University of Colorado at Boulder, supported by an NSF Graduate Research Fellowship.

My research applies a wide range of techniques from data science — from statistics and mathematical modeling to surveys and experimentation — toward the study of complex social systems, ranging from academic careers to human rights. My advisor is Aaron Clauset.

During my PhD, I was a (2x) research intern with the MSR NYC Computational Social Science group and a Data Science & Human Rights Fellow with HRDAG. Previously, I worked as a software consultant at Pivotal Labs, a software engineer at multiple startups including on a DARPA project, and as a Data Science for Social Good Fellow at the University of Chicago.

**I am organizing to improve public higher education with my labor union**, United Campus Workers Colorado, and currently serving my second term on the Executive Board of CWA 7799.

Pronouns: he/him.

Upcoming

**Fall 2023:**I will be visiting the Vermont Complex Systems Center at UVM until November, and giving talks at the UVM Statistics Colloquium, the UMass Amherst sociology department and the Vermont-KIAS workshop.

News

**Fall 2023:**New paper in*PLOS One*.**Summer 2023:**New paper in*PNAS*. Talks at the MIT Media Lab, ICERM, NetSci in Vienna, IC2S2 in Copenhagen, and the Academic Analytics Research Center. Honored to be a panelist on this NSF/AAAS event where five federal agencies laid out their public access plans for the first time. Attended the AMS Mathematics Research Community on Complex Social Systems and the Contagion on Complex Social Systems workshop at UVM.**Spring 2023:**New paper in*PNAS Nexus*. Talks at the Math for All Boulder satellite and the Atlanta Conference on Science and Innovation Policy.-
**Winter 2022:**New paper in*Communications of the ACM*. Talk at Dynamics Days US 2023. -
**Fall 2022:**New papers in*Science Advances*and*Nature*. In residence with the Human Rights Data Analysis Group in SF. -
**Summer 2022:**New paper in*Nature Communications*. Gave talks at ICSSI in DC and SoCG virtually in Berlin. Attended a science of science workshop at SFI, and participated in the SFI Complexity-GAINs International Summer School in Vienna. -
**Spring 2022:**Attended the Atlanta Academy on Science and Innovation Policy and the Aspen Center for Physics Dynamics of Social Interactions winter conference. Returned to MSR NYC for a second research internship.

Selected Publications

For full publications, see [CV] or [Google Scholar].

**S. Zhang**, P.R. Heck, M.N. Myers, C.F. Chabris, D.G. Goldstein, & J.M. Hofman.*PNAS*(2023).**S. Zhang**, N. LaBerge, S.F. Way, D.B. Larremore, & A. Clauset. Submitted (2023).**S. Zhang**, K.H. Wapman, D.B. Larremore, & A. Clauset.*Science Advances*(2022).-
K.H. Wapman,
**S. Zhang**, A. Clauset, & D.B. Larremore.*Nature*(2022).

Visualizations

I was drawn to study math because I found it to be beautiful.
I hope I can share some of that beauty through these interactive visualizations.
I made many of these visualizations to learn the concepts myself, but occasionally they are also part of larger projects.
*Note: many of these visualizations only work on desktop.*

An illusion of predictability in scientific results

Even experts think / that well-estimated means / are certain outcomes. (Haiku summary due to MSR poets Dan and Jake). Click the thumbnail for a mini-explainer.

Elliptic curves and traveling wave solutions to the KdV equations

View traveling wave solutions to the KdV equations associated with (points of) elliptic curves.

Bayesian inference for COVID-19 testing

My brief foray into epidemiology at the start of COVID-19. Bayesian methods and interactive tools for informing COVID-19 surveillance testing strategies.

A catastrophe machine

Move the center of gravity of a wedge balancing on a table, and observe its corresponding catastrophe surface.

Linear regression, the old fashioned way

Perform ordinary least squares through a set of points with nails, springs, sleeves, and a frictionless rod.

A moduli space for triangles

A solution to a problem by Lewis Carroll using a clever moduli space. For fun, pick points on the moduli space, and watch triangles deform between them along geodesics.

The cross-section of a cylinder is an ellipse

A classical proof that the cross-section of a cylinder is an ellipse. I have no idea why, but this is the most popular blog post on my website.

Whitney's Umbrella

First steps in visualizing 3d mathematics using javascript. A famous surface with a cuspidal point.

Voronoizer bookmarklet

Draw a Voronoi diagram over any webpage with this bookmarklet.

Voronoize this page!

This page has a Voronoi diagram drawn over it, with link and input HTML elements as points.

Treasure hunting

You have been given flawed instructions for finding treasure on an island, but geometry may be able to help.

An ascii implicit function plotter

Plot an elliptic curve (or any implicit function) using ASCII art!

Cats on ladders

A cat is sitting on a ladder leaning against the wall, and the ladder slips. What shape does the cat draw through the air?

A network look at integer sequences

The Online Encyclopedia of Integer Sequences (OEIS) from a 10,000 foot view.

A visualization of a geometric bound on convex hulls

A lemma that bounds the size of a convex hull of points based off circles centered at those points.

Building a municipal land use code search engine using a graph of word embeddings

Using the geometry of language to help permit-seekers find the right municipal land use codes.