IQIM Postdoctoral and Graduate Student Seminar

Friday, September 2, 2022
12:00pm to 1:00pm
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East Bridge 114
Discrete Bulk Reconstruction
Jason Pollack, Postdoctoral Scholar, University of Texas, Austin,

Abstract: In AdS/CFT, the Ryu-Takayanagi (RT) formula identifies the von Neumann entropy of a boundary region with the minimal area of any surface separating that region from its complement. This links AdS/CFT to the study of min-cuts in graph theory. If we model the spatial geometry discretely, via a weighted undirected graph with distinguished boundary vertices, then we can define a "discrete bulk reconstruction problem," wherein we're given the values of min-cuts separating certain sets of boundary vertices from other sets, and our goal is to find a graph consistent with those values. We study this task directly as a computational problem: when does the bulk graph exist? Can we upper-bound how many vertices it has? Can we ensure that it's planar, or embeddable on some other manifold? Can we construct the graph in polynomial time?

Lunch will be provided, following the talk, on the lawn outside the Bridge arcade.

Attendees joining in person must demonstrate that they comply with Caltech's vaccination requirements (Caltech ID or AWS ID required).

Amid the recent increase in COVID-19 cases on campus due to the arrival of the highly infectious BA.2 subvariant in Los Angeles County and a return to routine social activities, the Institute has reinstated its requirement that high-quality masks (surgical, N95s, KN95s, or KF95s) must be worn in all indoor locations on campus.

For more information, please contact Marcia Brown by phone at 626-395-4013 or by email at