SciPost Submission Page
Loops in 4+1d Topological Phases
by Xie Chen, Arpit Dua, Po-Shen Hsin, Chao-Ming Jian, Wilbur Shirley, Cenke Xu
This Submission thread is now published as
Submission summary
| Submission information |
| Preprint Link: |
scipost_202210_00089v1
(pdf)
|
| Date accepted: |
2023-01-10 |
| Date submitted: |
2022-10-30 23:54 |
| Submitted by: |
Dua, Arpit |
| Submitted to: |
SciPost Physics |
| Ontological classification |
| Academic field: |
Physics |
| Specialties: |
- Condensed Matter Physics - Theory
- High-Energy Physics - Theory
|
| Approach: |
Theoretical |
Abstract
2+1d topological phases are well characterized by the fusion rules and braiding/exchange statistics of fractional point excitations. In 4+1d, some topological phases contain only fractional loop excitations. What kind of loop statistics exist? We study the 4+1d gauge theory with 2-form $\mathbb{Z}_2$ gauge field (the loop only toric code) and find that while braiding statistics between two different types of loops can be nontrivial, the self `exchange' statistics are all trivial. In particular, we show that the electric, magnetic, and dyonic loop excitations in the 4+1d toric code are not distinguished by their self-statistics. They tunnel into each other across 3+1d invertible domain walls which in turn give explicit unitary circuits that map the loop excitations into each other. The $SL(2,\mathbb{Z}_2)$ symmetry that permutes the loops, however, cannot be consistently gauged and we discuss the associated obstruction in the process. Moreover, we discuss a gapless boundary condition dubbed the `fractional Maxwell theory' and show how it can be Higgsed into gapped boundary conditions. We also discuss the generalization of these results from the $\mathbb{Z}_2$ gauge group to $\mathbb{Z}_N$.
