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Qiuzhen College, Tsinghua University
Yau Mathematical Sciences Center, Tsinghua University (YMSC)
Tsinghua Sanya International  Mathematics Forum (TSIMF)
Shanghai Institute for Mathematics and  Interdisciplinary Sciences (SIMIS)
Hetao Institute of Mathematics and Interdisciplinary Sciences
BIMSA > An operator-algebraic approach to phase of matters
An operator-algebraic approach to phase of matters
In one-dimensional quantum lattice systems, localized charges are naturally described by C*-correspondences rather than only by representations or endomorphisms. This research-oriented topics course develops Corey Jones’s DHR bimodule theory and its applications to fusion spin chains, quantum cellular automata, half-line charge categories, and categorical symmetry.

The first part establishes the required foundations: C*-algebras and quasi-local nets, unitary tensor categories and Drinfeld centers, Hilbert C*-modules and correspondences, C*-2-categories, Q-systems, finite-index conditional expectations, and Q-system realization. We then construct the C*-tensor category of localized and transportable DHR bimodules, its unitary braiding, and its functoriality under bounded-spread isomorphisms. For fusion spin chains, this leads to the braided equivalence between the DHR category and the Drinfeld center of the underlying fusion category.

The course next studies the Jones–Lim index for quantum cellular automata as a numerical measure of information flow complementary to the induced action on DHR sectors. We then construct intrinsic half-line charge categories and analyze the hypotheses under which their Drinfeld center recovers the DHR category. The final part develops the operator-algebraic SymTFT picture through physical-boundary inclusions, Lagrangian Q-systems, solitonic bimodules, and categorical symmetries realized by locality-preserving quantum channels. Applications include tensor-product and on-site realizability, symmetric states, anomaly-enforced gaplessness, and local topological order.

The course emphasizes detailed proofs of central results, concrete examples, and guided reading of recent research papers.
Lecturer
Quan Chen
Date
14th September ~ 7th December, 2026
Location
Weekday Time Venue Online ID Password
Monday 08:50 - 12:15 A3-3-301 Zoom 17 442 374 5045 BIMSA
Prerequisite
mathematical maturity and familiarity with graduate algebra and Hilbert spaces. Prior exposure to functional analysis is recommended. No previous knowledge of tensor categories, DHR theory, or categorical symmetry is assumed.
Syllabus
Week 1. C*-algebras
Week 2. Unitary tensor categories I
Week 3. Unitary tensor categories II
Week 4. C*-correspondences and C*-2-categories
Week 5. Q-systems, finite index, and realization
Week 6. Abstract DHR bimodule theory
Week 7. Fusion spin chains and the center theorem
Week 8. Index theory for quantum cellular automata
Week 9. Half-line charge categories I
Week 10. Half-line charge categories II
Week 11. Physical boundaries and operator-algebraic SymTFT
Week 12. Categorical symmetry and applications
Audience
Undergraduate , Advanced Undergraduate , Graduate , Postdoc , Researcher
Video Public
Yes
Notes Public
Yes
Language
English
Lecturer Intro
Quan Chen has been an assistant professor at BIMSA since June 2026. He was a postdoctoral researcher at Vanderbilt University, where he began his position in Fall 2023 under the mentorship of Professor Dietmar Bisch. He earned his Ph.D. in Mathematics from The Ohio State University in Spring 2023, working under the supervision of Professor David Penneys. His research interests lie in the areas of operator algebras, subfactor theory, and quantum algebra.
Beijing Institute of Mathematical Sciences and Applications
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