Group theory in spectroscopy

1 Symmetry may be viewed either as beautiful or primitive. It seems that from the psychological point of view, the symmetry stresses people’s longing for simplicity, order, and understanding. On the other hand, symmetry means less information and hence often a kind of wearingly dull stimuli. Possibly an interplay of these two opposite features leads us to consider as beautiful what has a broken symmetry. The trees and the leaves exhibit broken symmetry and look beautiful. Ancient architects knew the secrets of creating beautiful buildings, which relied on symmetry breaking, which is substantial but almost invisible from distance. 2 g may be finite or infinite. In practical applications in this Appendix, g will be always finite.