Abstract
The first problems in this chapter deal with basic properties of groups and of group representations. Fundamental results following from Schur lemma are introduced since the beginning in the case of finite groups, with simple applications of character theory, in the study of vibrational levels of symmetric systems. Other problems concern the notion and properties of Lie groups and Lie algebras, mainly oriented to physical examples: rotation groups \({ SO}_2\), \(SO_3\), \(SU_2\), translations, Euclidean group, Lorentz transformations, dilations, Heisenberg group, \(SU_3\), with their physically relevant representations. The last section starts with some examples and applications of symmetry properties of differential equations, provides a group-theoretical interpretation of the Zeeman and Stark effects, and finally is devoted to obtaining the symmetry properties of the hydrogen atom (the group \({ SO}_4\)) and of the three-dimensional harmonic oscillator (the group \(U_3\)) in quantum mechanics.
This is a preview of subscription content, log in via an institution.
Buying options
Tax calculation will be finalised at checkout
Purchases are for personal use only
Learn about institutional subscriptionsNotes
- 1.
It can be useful to recall that, according to Ado theorem, all finite-dimensional Lie algebras admit a faithful representation by means of matrices.
- 2.
It is customary in physics to introduce a factor i in the definition of these generators, in order to have Hermitian operators. For example, \(A=-i\, d/dx\), which is proportional to the momentum operator \(P=-i\hbar \, d/dx\) in quantum mechanics, as well known.
- 3.
\(\mathscr {L}\) is the subgroup “connected to the identity” of the full Lorentz group, usually denoted by O(3, 1), which includes also space inversions and time reversal. The same remark holds for the group considered in q. (1), which is a subgroup of O(2, 1).
- 4.
It can be useful to point out that, differently from all the groups \(SU_n\) with \(n>2\), the “basic” irreducible representations \({\mathscr {R}}\) and \({\mathscr {R}}^*\) of \(SU_2\) by means of \(2\times 2\) unitary matrices are equivalent.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
Copyright information
© 2018 Springer International Publishing AG, part of Springer Nature
About this chapter
Cite this chapter
Cicogna, G. (2018). Groups, Lie Algebras, Symmetries in Physics. In: Exercises and Problems in Mathematical Methods of Physics. Undergraduate Lecture Notes in Physics. Springer, Cham. https://doi.org/10.1007/978-3-319-76165-7_4
Download citation
DOI: https://doi.org/10.1007/978-3-319-76165-7_4
Published:
Publisher Name: Springer, Cham
Print ISBN: 978-3-319-76164-0
Online ISBN: 978-3-319-76165-7
eBook Packages: Physics and AstronomyPhysics and Astronomy (R0)