Sökning: "vertex function"

Visar resultat 1 - 5 av 20 avhandlingar innehållade orden vertex function.

  1. 1. Model Vertices Beyond the GW Approximation

    Författare :Mikael Hindgren; Matematisk fysik; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Matematisk och allmän teoretisk fysik; thermodynamics; statistical physics; gravitation; GW approximation; Electron self energy; Green s function; consistency; local-field corrections; vertex function; conserving approximations; variational energies; Mathematical and general theoretical physics; classical mechanics; relativity; quantum mechanics; klassisk mekanik; kvantmekanik; relativitet; statistisk fysik; termodynamik; Fysicumarkivet A:1997:Hindgren;

    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

  3. 2. First principles methods for electronic structure calculations of solids

    Författare :Martin Springer; Matematisk fysik; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; screened interaction; T-matrix; vertex function; GW approximation; Green function; density functional theory; gradient expansion; order N method; Physics; Fysik;

    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

  4. 3. Twisting and Gluing : On Topological Field Theories, Sigma Models and Vertex Algebras

    Författare :Johan Källén; Maxim Zabzine; Mathias Blau; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Topological field theory; Chern-Simons theory; Contact geometry; Sigma models; Poisson vertex algebras; Vertex algebras; String theory; Theoretical Physics; Teoretisk fysik;

    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

  5. 4. Dualities, affine vertex operator algebras, and geometry of complex polynomials

    Författare :Julius Borcea; Matematik (naturvetenskapliga fakulteten); []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Sendov s conjecture; annihilating fields; relative vertex operators; twisted modules; vertex operator algebras; Affine Lie algebras; standard modules; geometry of polynomials.; Mathematics; Matematik;

    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

  7. 5. A combinatorial description of certain polynomials related to the XYZ spin chain

    Författare :Linnea Hietala; Göteborgs universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; six-vertex model; eight-vertex SOS model; three-color model; domain wall boundary conditions; reflecting end; partition function; determinant formula; XYZ spin chain; alternating sign matrices; polynomials; positive coefficients;

    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