Sökning: "vertex function"
Visar resultat 1 - 5 av 20 avhandlingar innehållade orden vertex function.
1. Model Vertices Beyond the GW Approximation
Sammanfattning : We study the effects of local vertex corrections to the self energy of the electron gas. We find that a vertex derived from time-dependent density-functional theory can give accurate self energies without including the explicit time dependence of the exchange-correlation potential provided, however, that a proper decay at large momentum transfer (large q) is built into the vertex function. LÄS MER
2. First principles methods for electronic structure calculations of solids
Sammanfattning : A straightforward gradient expansion of the exchange energy of a perturbed electron gas is performed. Studied perturbations range from very weak to those that produce, e.g., a silicon-like band structure with a band gap. LÄS MER
3. Twisting and Gluing : On Topological Field Theories, Sigma Models and Vertex Algebras
Sammanfattning : This thesis consists of two parts, which can be read separately. In the first part we study aspects of topological field theories. We show how to topologically twist three-dimensional N=2 supersymmetric Chern-Simons theory using a contact structure on the underlying manifold. LÄS MER
4. Dualities, affine vertex operator algebras, and geometry of complex polynomials
Sammanfattning : This thesis consists of two parts which deal with different subjects. In the first part we study certain aspects of the representation theory of affine Kac-Moody Lie algebras and related structures. LÄS MER
5. A combinatorial description of certain polynomials related to the XYZ spin chain
Sammanfattning : The aim of this thesis is to study the connection between the three-color model and the polynomials q_n(z) of Bazhanov and Mangazeev. To give some background, we describe some exactly solvable, quantum integrable lattice models and their connections to each other and to other models. LÄS MER