33.2

33.4; timescales, 33.3; pointer basis, 33.3; and measurement, 33.4 Degeneracy, **3.4**, 5.5; accidental, 5.5, 9.4; essential, 5.5; lifting of, 18.1 Degenerate perturbation theory, **18.1**--18.4; algorithm, 18.1; fine structure, 18.2 Delta function potential, **3.4** Density matrix, **23.1**--23.5;