Entangled graphs on surfaces in space

dc.contributor.authorCastle, Toen
dc.date.accessioned2014-08-27T23:38:28Z
dc.date.available2014-08-27T23:38:28Z
dc.date.issued2013
dc.description.abstractIn the chemical world, as well as the physical, strands get tangled. When those strands form loops, the mathematical discipline of ‘knot theory’ can be used to analyse and describe the resultant tangles. However less has been studied about the situation when the strands branch and form entangled loops in either finite structures or infinite periodic structures. The branches and loops within the structure form a ‘graph’, and can be described by mathematical ‘graph theory’, but when graph theory concerns itself with the way that a graph can fit in space, it typically focuses on the simplest ways of doing so. Graph theory thus provides few tools for understanding graphs that are entangled beyond their simplest spatial configurations. This thesis explores this gap between knot theory and graph theory. It is focussed on the introduction of small amounts of entanglement into finite graphs embedded in space. These graphs are located on surfaces in space, and the surface is chosen to allow a limited amount of complexity. As well as limiting the types of entanglement possible, the surface simplifies the analysis of the problem – reducing a three-dimensional problem to a two-dimensional one. Through much of this thesis, the embedding surface is a torus (the surface of a doughnut) and the graph embedded on the surface is the graph of a polyhedron. Polyhedral graphs can be embedded on a sphere, but the addition of the central hole of the torus allows a certain amount of freedom for the entanglement of the edges of the graph. Entanglements of the five Platonic polyhedra (tetrahedron, octahedron, cube, dodecahedron, icosahedron) are studied in depth through their embeddings on the torus. The structures that are produced in this way are analysed in terms of their component knots and links, as well as their symmetry and energy. It is then shown that all toroidally embedded tangled polyhedral graphs are necessarily chiral, which is an important property in biochemical and other systems. These finite tangled structures can also be used to make tangled infinite periodic nets; planar repeating subgraphs within the net can be systematically replaced with a tangled version, introducing a controlled level of entanglement into the net. Finally, the analysis of entangled structures simply in terms of knots and links is shown to be deficient, as a novel form of tangling can exist which involves neither knots nor links. This new form of entanglement is known as a ravel. Different types of ravels can be localised to the immediate vicinity of a vertex, or can be spread over an arbitrarily large scope within a finite graph or periodic net. These different forms of entanglement are relevant to chemical and biochemical self-assembly, including DNA nanotechnology and metal-ligand complex crystallisation.en_AU
dc.identifier.otherb35683934
dc.identifier.urihttp://hdl.handle.net/1885/11978
dc.language.isoen_AUen_AU
dc.subjectgeometryen_AU
dc.subjecttopologyen_AU
dc.subjectentanglementen_AU
dc.subjectchiralityen_AU
dc.subjectknotsen_AU
dc.subjectlinksen_AU
dc.subjectravelsen_AU
dc.subjectplatonic polyhedraen_AU
dc.subjectcubeen_AU
dc.subjecttetrahedronen_AU
dc.subjectoctahedronen_AU
dc.subjecttoroidal embeddingen_AU
dc.titleEntangled graphs on surfaces in spaceen_AU
dc.typeThesis (PhD)en_AU
local.contributor.affiliationResearch School of Physics, Department of Mathematicsen_AU
local.contributor.authoremailtoen.castle@anu.edu.auen_AU
local.contributor.authoremailtoen.castle@gmail.comen_AU
local.contributor.supervisorHyde, Stephen
local.contributor.supervisorcontactstephen.hyde@anu.edu.au
local.identifier.doi10.25911/5d7391e72cdc9
local.mintdoimint
local.type.degreeDoctor of Philosophy (PhD)en_AU

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