Exploring 2-group global symmetries
- Inst. for Advanced Study, Princeton, NJ (United States)
- Harvard Univ., Cambridge, MA (United States); Univ. of California, Los Angeles, CA (United States)
- Univ. of California, San Diego, La Jolla, CA (United States)
Here, we analyze four-dimensional quantum field theories with continuous 2-group global symmetries. At the level of their charges, such symmetries are identical to a product of continuous flavor or spacetime symmetries with a 1-form global symmetry U(1)B(1), which arises from a conserved 2-form current JB(2). Rather, 2-group symmetries are characterized by deformed current algebras, with quantized structure constants, which allow two flavor currents or stress tensors to fuse into JB(2). This leads to unconventional Ward identities, which constrain the allowed patterns of spontaneous 2-group symmetry breaking and other aspects of the renormalization group flow. If JB(2) is coupled to a 2-form background gauge field B(2), the 2-group current algebra modifies the behavior of B(2) under background gauge transformations. Its transformation rule takes the same form as in the Green-Schwarz mechanism, but only involves the background gauge or gravity fields that couple to the other 2-group currents. This makes it possible to partially cancel reducible ’t Hooft anomalies using Green-Schwarz counterterms for the 2-group background gauge fields. The parts that cannot be cancelled are reinterpreted as mixed, global anomalies involving U(1)B(1), which receive contributions from topological, as well as massless, degrees of freedom. Theories with 2-group symmetry are constructed by gauging an abelian flavor symmetry with suitable mixed ’t Hooft anomalies, which leads to many simple and explicit examples. Some of them have dynamical string excitations that carry U(1)B(1) charge, and 2-group symmetry determines certain ’t Hooft anomalies on the world sheets of these strings. Lastly, we point out that holographic theories with 2-group global symmetries have a bulk description in terms of dynamical gauge fields that participate in a conventional Green-Schwarz mechanism.
- Research Organization:
- Institute for Advanced Study, Princeton, NJ (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC); National Science Foundation (NSF); John Templeton Foundation
- Grant/Contract Number:
- SC0009988; SC0009919; PHY-1719924; 52476
- OSTI ID:
- 1598254
- Journal Information:
- Journal of High Energy Physics (Online), Vol. 2019, Issue 2; ISSN 1029-8479
- Publisher:
- Springer BerlinCopyright Statement
- Country of Publication:
- United States
- Language:
- English
Web of Science
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Related Subjects
symmetry: global
anomaly: Green-Schwarz
symmetry: flavor
symmetry: space-time
flavor: 2
transformation: gauge
renormalization group: flow
string: excited state
tensor: energy-momentum
dimension: 4
background
gauge field theory
current algebra
field theory
symmetry breaking
conservation law
Ward identity
quantization
gravitation
topological
deformation
holography
abelian
U(1)