Liouville invariance in quantum and classical mechanics
Alec Maassen van den Brink
Alexandre Zagoskin
2134/19899
https://repository.lboro.ac.uk/articles/journal_contribution/Liouville_invariance_in_quantum_and_classical_mechanics/9408326
The density-matrix and Heisenberg formulations of quantum mechanics follow--for unitary evolution--directy from the Schr"odinger equation. Nevertheless, the symmetries of the corresponding evolution operator, the Liouvillian L=i[.,H], need not be limited to those of the Hamiltonian H. This is due to L only involving eigenenergy_differences_, which can be degenerate even if the energies themselves are not. Remarkably, this possibility has rarely been mentioned in the literature, and never pursued more generally. We consider an example involving mesoscopic Josephson devices, but the analysis only assumes familiarity with basic quantum mechanics. Subsequently, such _L-symmetries_ are shown to occur more widely, in particular also in classical mechanics. The symmetry's relevance to dissipative systems and quantum-information processing is briefly discussed.
2015-12-17 11:28:25
Symmetry
Superoperators
Phase-space flow
Quantum Mechanics
Physical Sciences not elsewhere classified
Computation Theory and Mathematics