# Symmetry in physics

2022/2023
Programme:
Physics, Second Cycle
Orientation:
Meteorology
Year:
2 year
Semester:
first or second
Kind:
optional
ECTS:
7
Language:
slovenian
Hours per week – 1. or 2. semester:
Lectures
2
Seminar
0
Tutorial
1
Lab
0
Content (Syllabus outline)

Groups. Role of symmetry in physics; examples.
Definition of group, group properties.
Examples: discrete groups (point groups, C2, C3, D3, D3h; permutation group, S3; continuous groups, R2, R3). Isomorphism, subgroup, direct product; conjugate elements, classes.
Representations of finite groups. Invariant subspaces, irreducibility, equivalent representations, Maschke theorem.
Orthogonality properties of irreducible
representations, Schur lemmas, orthogonality
relations, examples. Characters of representations, orthogonality relations for characters of irreducible representations, reduction of representations, irreducibility criterion. Regular representation. Construction of character table. Subduction. Projection operators. Wigner-Eckart theorem.
Symmetry in quantum mechanics. Labelling of degenerate electron states, selection rules, variational solution of quantum-mechanical problems, perturbation theory.
Molecular vibrations. Classical vibration modes,
classification of normal modes, vibration
patterns, vibrational levels and wave functions
(ground state, fundamental states, combined
states).
Crystallographic point groups. Stereogram,
proper groups, improper groups, class
structure of point groups. Point and
translational symmetry. Crystal systems.
Irreducible representations.
Atom in crystal field. Spin and double group. Splitting of atomic levels in weak and moderate crystal field.
Continuous groups. Infinitesimal operators, Lie algebras, Unitary representations, Wigner-Eckart theorem for continuous groups, irreducible representations, adjoint representation, simple algebras and groups. Examples: R2, R3, SU(2), SU(3).
Construction of irreducible representations of continuous groups. Casimir operators, Cartan subalgebra, roots and weights, positive weights, simple roots, fundamental representations, Dynkin indices and diagrams. Particle physics examples: SU(3) in QCD.
Tensor methods in SU(3). Invariant tensors, decomposition of product representations, Young tableaux and SU(3): dimension of representation, product representations. Particle-physics examples: Flavor symmetry of light quarks and spectra of hadronic states.
Space and time. Lorentz transformations, Lorentz group, generators of SO(3,1). Examples of representations of Lorentz group: Dirac representation. Translations, Poincare group and its representations for massive and massless particles. Coleman-Mandula theorem and supersymmetry.

W. Ludwig in C. Falter, Symmetries in Physics, Springer, Berlin, 1996,
J. P. Elliott in P. G. Dawber, Symmetry in Physics, MacMillan, Houndmills, 1979,
M. Hamermesh, Group Theory and Its Application to Physical Problems, Dover, New York, 1989,
M. Tinkham, Group Theory and Quantum Mechanics, McGraw Hill, New York, 1964,
S. K. Kim, Group Theoretical Methods and Applications to Molecules and Crystals, Cambridge University Press, Cambridge, 1999,
W.-K. Tung, Group Theory in Physics, World Scientific, Singapore, 1985,
F. Stancu, Group Theory in Subnuclear Physics, Oxford Science Publications, Oxford, 1996,
H. Georgi, Lie algebras in particle physics, Westview Press, Boulder, CO, 1999.

Objectives and competences

To provide a balanced overview of the role of symmetry in physical systems using a selection of examples from physics of elementary particles, atomic and molecular physics as well as condensed-matter physics, and to introduce the group theory and the theory of representations as tools for the description of symmetry.

Intended learning outcomes

Knowledge and understanding
To master the methods of group theory and to understand the role of symmetry in physics. To gain an overview of various physical systems that are as illustrative as possible from the group-theory perspective, thereby complementing the phenomenological insight into the physics of elementary particles, atoms, molecules, and condensed matter provided by the respective specialized courses.

Application
Students learn to use the methods of group theory, especially the theory of representations, to study symmetry in various physical systems.

Reflection
The course helps to appreciate the meaning of symmetry as a factor that constrains and systemizes the set of possible states of physical systems. As it builds on examples from a range of branches of physics, it offers an overview of formally similar yet distinct phenomena.

Transferable skills
Identification of aspects of physical problems that can be studied using group theory.

Learning and teaching methods

lectures, tutorials, seminars, homework assignments, consultations

Assessment

completed homework assignment (written report, presentation) counts as problem-solving examination
oral examination
grading: 1-5 (fail), 6-10 (pass) (according to the Statute of UL)

Lecturer's references

doc. dr. J. Fesel Kamenik
1. HURTH, Tobias, ISIDORI, Gino, KAMENIK, Jernej, MESCIA, Federico. Constraints on new physics in MFV models : a model-independent analysis of [Delta]F=1 processes. Nuclear physics. Section B, ISSN 0550-3213. [Print ed.], 2009, vol. 808, no. 1/2, str. 326-346. [COBISS-SI-ID 22772007].
2. DORŠNER, Ilja, FAJFER, Svjetlana, KAMENIK, Jernej, KOŠNIK, Nejc. Light colored scalars from grand unification and the forward-backward asymmetry in t[bar]t production. Physical review. D, Particles, fields, gravitation, and cosmology, ISSN 1550-7998, 2010, vol. 81, no. 5, str. 055009-1-055009-11. [COBISS-SI-ID 23517735].
3. DROBNAK, Jure, FAJFER, Svjetlana, KAMENIK, Jernej. Probing anomalous t W b interactions with rare B decays. Nuclear physics. Section B, ISSN 0550-3213. [Print ed.], 2011, vol. 855, no. 1, str. 82-99, doi: 10.1016/j.nuclphysb.2011.10.004. [COBISS-SI-ID 25202215].
4. GEDALIA, Oram, KAMENIK, Jernej, LIGETI, Zoltan, PEREZ, Gilad. On the universality of CP violation in [delta]F = 1 processes. Physics letters. Section B, ISSN 0370-2693. [Print ed.], 2012, vol. 714, no. 1, str. 55-61, doi: 10.1016/j.physletb.2012.06.050. [COBISS-SI-ID 25960999].
5. FAJFER, Svjetlana, KAMENIK, Jernej, NIŠANDŽIĆ, Ivan, ZUPAN, Jure. Implications of lepton flavor universality violations in B decays. Physical review letters, ISSN 0031-9007. [Print ed.], 2012, vol. 109, issue 16, str. 161801-1-161801-5, doi: 10.1103/PhysRevLett.109.161801. [COBISS-SI-ID 26186535].
izr. prof. dr. P. Ziherl
1. DOTERA, T., OSHIRO, T, ZIHERL, Primož. Mosaic two-lengthscale quasicrystals. Nature, ISSN 0028-0836, 2014, vol. 506, no. 7487, str. 208-211, doi: 10.1038/nature12938. [COBISS-SI-ID 27499815].
2. GLASER, M. A., GRASON, G. M., KAMIEN, Randall D., KOŠMRLJ, Andrej, SANTANGELO, C. D., ZIHERL, Primož. Soft spheres make more mesophases. Europhysics letters, ISSN 0295-5075, 2007, vol. 78, str. 46004-1-46004-5. [COBISS-SI-ID 20719143].
3. ZIHERL, Primož, KAMIEN, Randall D. Soap froths and crystal structures. Physical review letters, ISSN 0031-9007. [Print ed.], 2000, vol. 85, str. 3528-3531. [COBISS-SI-ID 15476775].
4. HOČEVAR BREZAVŠČEK, Ana, EL SHAWISH, Samir, ZIHERL, Primož. Morphometry and structure of natural random tilings. The European physical journal. E, Soft matter, ISSN 1292-8941, 2010, vol. 33, no. 4, str. 369-375. [COBISS-SI-ID 24277287].
5. HOČEVAR BREZAVŠČEK, Ana, ZIHERL, Primož. Periodic three-dimensional assemblies of polyhedral lipid vesicles. Physical review. E, Statistical, nonlinear, and soft matter physics, ISSN 1539-3755, 2011, vol. 83, no. 4, str. 041917-1-041917-10. [COBISS-SI-ID 24719655].