Emilio Zappa. New group theoretical methods for applications in virology and quasicrystals. New York, University of York, 2015.

Non-crystallographic symmetries are ubiquitous in physics, chemistry and biology. Prominent examples are quasicrystals, alloys with long-range order but no translational periodicity in their atomic organisation, and viruses, micro-organisms consisting of a protein shell, the capsid, that in most cases displays icosahedral symmetry. Group theory plays a crucial role in understanding their structures and their physical and geometrical properties. In this thesis new group theoretical methods are introduced, to characterise virus organisation and model structural transitions of icosahedral quasicrystals.