9/26 ADS Seminar:
Speaker: Jing-Yuan Chen （IASTU）
Title: Instanton in Lattice QCD from Higher Category Theory

Abstract: A long standing problem in lattice QCD is to find a natural definition of instanton operator on the lattice. I will show how this problem is -- and has to be -- solved by higher category theory. In this language, the solution is a deep generalization of the Villain model familiar in condensed matter physics and in lattice Maxwell. Using the particular categorical structure, one can define 2d Wess-Zumino-Witten term, 3d skrymion and 4d hedgehog in lattice S^3 (pion) non-linear sigma model, and 3d Chern-Simons term, 4d instanton and 5d Yang monopole in lattice Yang-Mills.

In a larger scope, I will sketch a systematic program towards rethinking the relation between continuum QFT and lattice QFT. As a result, all topological operators can be naturally defined on the lattice. I will discuss what implications this might have on the understanding of renormalization, the relation between dynamical and topological QFT (in particular, going beyond the well-developed tensor category formalism which only deals with discrete degrees of freedom, and find a unifying language that emcompases the more physical continuous degrees of freedom), and the program of constructive QFT.

Time：26/09/2024 1:30 pm Qiuzhen Hall, Ningzhai 

ADS seminar this coming Thursday
Speaker : Wei Wang (TD Lee Institute, Jiaotong University)
Title: Building holographic code from the boundary.                                                

Abstract: Holographic quantum error-correcting code, the quantum-information structure hypothesized for the AdS/CFT correspondence, has being attracting increasing attention in new directions interrelating the studies of quantum gravity and quantum simulation. In this work, we initiate a novel approach for building holographic code that can be generally applied in potentially broad and interdisciplinary contexts. Our approach takes an “opposite” route to the conventional paradigm that is based on bulk tensor-networks. As illustrated in an exact model, we start from scalable descriptions of boundary qudits which can guide succinct quantum-circuit simulations, and rigorously show how the bulk qudits and the encoding structure emerge from boundary entanglement patterns. By investigating the entanglement patterns, we systematically unfold the hypothetical structure for bulk reconstruction and the details of the Ryu-Takayanagi formula in the formalism of operator-algebra quantum error correction, demonstrating desired properties that are not yet proved in the established models. Our work might offer a fresh perspective for the study of holographic code.                                                                                      

Bio: Wei Wang obtained his Ph.D. in Physics from University of Oklahoma (U.S.) in 2017. Then he worked as a postdoc in Max Planck Institute for the Physics of Complex Systems (Germany). Now he is an independent postdoc in Tsung-Dao Lee Institute, Shanghai Jiao Tong university. His current work primarily focuses on interdisciplinary research at the intersection of quantum information, condensed matter physics, and high-energy physics.
Time: Thur., 13:30-15:05, Sept. 19, 2024 (THIS THURSDAY)
Venue: Qiuzhen Hall, Ningzhai (Inside Tsinghua main campus)
(please contact us if you need help getting into campus)