The axial symmetry U ( 1 ) is exact in the classical theory , but broken in the quantum theory , an occurrence called an anomaly .
The vector symmetry , U ( 1 ) corresponds to the baryon number of quarks and is an exact symmetry .
The axial symmetry U ( 1 ) is exact in the classical theory , but broken in the quantum theory , an occurrence called an anomaly .
The vector symmetry , U ( 1 ) corresponds to the baryon number of quarks and is an exact symmetry .