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Hidden antiunitary symmetry behind “accidental” degeneracy and its protection of degeneracy |
Jing-Min Hou1(), Wei Chen2 |
1. School of Physics, Southeast University, Nanjing 211189, China 2. College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China |
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Abstract In quantum mechanics, accidental degeneracy refers to energy degeneracy that occurs coincidentally, without any protection by symmetry. Here, we prove a theorem stating that any two-fold degeneracy (accidental or not) in a quantum system is protected by a novel hidden symmetry, which can be expressed by an antiunitary operator with its square being −1. In this sense, the so-called accidental degeneracy is not really accidental, and this actually implies a hidden antiunitary symmetry.
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Keywords
accidental degeneracy
hidden symmetry
antiunitary symmetry
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Corresponding Author(s):
Jing-Min Hou
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Issue Date: 22 September 2017
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