  In the early 2000s, the study of time operators advanced as one of the
methods to understand the problem of time as mathematical science. However, the
starting point for the time operator is to understand time as a problem of
observation (the survival probabilityof particles), and today, even after the
issue of representation on time operator has concluded, the question of
philosophical interpretation still exists. Furthermore, when it comes to the
question of how time generation (emergence), the method of time operators has
its limitations. Regarding the generation of time, symmetry breaking in
particle physics seems to be closely related.
