Search for dissertations about: "Function approximation"

Showing result 1 - 5 of 223 swedish dissertations containing the words Function approximation.

  1. 1. Model Vertices Beyond the GW Approximation

    Author : Mikael Hindgren; Matematisk fysik; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; 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;

    Abstract : 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. READ MORE

  2. 2. Approximation and Subextension of Negative Plurisubharmonic Functions

    Author : Lisa Hed; Urban Cegrell; Frank Wikström; Umeå universitet; []
    Keywords : NATURAL SCIENCES; NATURVETENSKAP; Complex Monge-Ampère operator; Approximation; Plurisubharmonic function; Subextension; MATHEMATICS; MATEMATIK;

    Abstract : In this thesis we study approximation of negative plurisubharmonic functions by functions defined on strictly larger domains. We show that, under certain conditions, every function u that is defined on a bounded hyperconvex domain Ω in Cn and has essentially boundary values zero and bounded Monge-Ampère mass, can be approximated by an increasing sequence of functions {uj} that are defined on strictly larger domains, has boundary values zero and bounded Monge-Ampère mass. READ MORE

  3. 3. Approximation of pluricomplex Green functions : A probabilistic approach

    Author : Azza Alghamdi; Maciej Klimek; Kaj Nyström; Anna Zdunik; Uppsala universitet; []
    Keywords : NATURAL SCIENCES; NATURVETENSKAP; pluricomplex Green function; pluriregular sets; Bernstein-Markov property; Bergman function; nearly orthonormal polynomials; orthogonal polynomials; Monte Carlo simulation; composite Julia sets; Julia sets; iterated function systems; the chaos game.;

    Abstract : This PhD thesis focuses on probabilistic methods of approximation of pluricomplex Green functions and is based on four papers.The thesis begins with a general introduction to the use of pluricomplex Green functions in multidimensional complex analysis and a review of their main properties. READ MORE

  4. 4. The plurisubharmonic Mergelyan property

    Author : Lisa Hed; Urban Cegrell; Anders Fällström; Per Åhag; Jan Wiegerinck; Umeå universitet; []
    Keywords : NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; Complex Monge-Ampère operator; approximation; plurisubharmonic function; subextension; Mergelyan property; plurisubharmonic function on compact sets; Jensen measures; Mathematics; matematik;

    Abstract : In this thesis, we study two different kinds of approximation of plurisubharmonic functions. The first one is a Mergelyan type approximation for plurisubharmonic functions. READ MORE

  5. 5. Studies of the Boundary Behaviour of Functions Related to Partial Differential Equations and Several Complex Variables

    Author : Håkan Persson; Kaj Nyström; Maciej Klimek; Evgeny Poletsky; Uppsala universitet; []
    Keywords : NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; uniformly parabolic equations; non-linear parabolic equations; linear growth; Lipschitz domain; NTA-domain; Riesz measure; boundary behavior; boundary Harnack; degenerate parabolic; parabolic measure; plurisubharmonic functions; continuous boundary; hyperconvexity; bounded exhaustion function; Hölder for all exponents; log-lipschitz; boundary regularity; approximation; Mergelyan type approximation; plurisubharmonic functions on compacts; Jensen measures; monotone convergence; plurisubharmonic extension; plurisubharmonic boundary values; Mathematics; Matematik;

    Abstract : This thesis consists of a comprehensive summary and six scientific papers dealing with the boundary behaviour of functions related to parabolic partial differential equations and several complex variables.Paper I concerns solutions to non-linear parabolic equations of linear growth. READ MORE