Symmetries which are only present at low temperatures are called [[accidental symmetry|accidental symmetries]]. For example, a symmetry which is broken by a process which requires a lot of energy, such as the creation of heavy [[virtual particles]], is an accidental symmetry at temperatures sufficiently low that this process is suppressed. | Symmetries which are only present at low temperatures are called [[accidental symmetry|accidental symmetries]]. For example, a symmetry which is broken by a process which requires a lot of energy, such as the creation of heavy [[virtual particles]], is an accidental symmetry at temperatures sufficiently low that this process is suppressed. |