Sökning: "Perturbation theory"

Visar resultat 1 - 5 av 147 avhandlingar innehållade orden Perturbation theory.

  1. 1. Multiconfigurational perturbation theory

    Författare :Kerstin Andersson; Karlstads universitet; []
    Nyckelord :Electron correlation; CASSCF; multiconfigurational second-order perturbation theory; CASPT2; ozone; C; N; O; F; Si; P; S; Cl; Ni; benzene; pyridine; pyrazine; pyrimidine; pyridazine; s-triazine; electric properties; excited states; spectroscopic data;

    Sammanfattning : The aim of the thesis is to analyze a method which describes the electron correlation in atoms and molecules. The method is based on Rayleigh-Schrödinger perturbation theory with a partitioning of the Hamiltonian into a fairly simple zeroth-order operator and a perturbation operator. LÄS MER

  3. 2. Topics in perturbation theory : From IBP identities to integrands

    Författare :Alessandro Georgoudis; Joseph A. Minahan; Tristan McLoughlin; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Perturbation theory; Feynman Integrals; Integrable field theories; Correlation functions.; Theoretical Physics; Teoretisk fysik;

    Sammanfattning : In this thesis we present different topics in perturbation theory. We start by introducing the method of integration by parts identities, which reduces a generic Feynman integral to a linear combination of a finite basis of master integrals. LÄS MER

  4. 3. The Powers of Perturbation Theory : Loops and Gauge Invariance in Particle Physics

    Författare :Johan Löfgren; Rikard Enberg; Kimmo Kainulainen; Uppsala universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Beyond the Standard Model; Electroweak phase transition; Perturbation theory; High Energy Physics; Högenergifysik;

    Sammanfattning : The Standard Model is the best particle physics theory we have, but there are still phenomena that it cannot explain. In this thesis I have worked on two different projects that connect to two of the biggest unsolved questions of the Standard Model. LÄS MER

  5. 4. Robust inference of gene regulatory networks : System properties, variable selection, subnetworks, and design of experiments

    Författare :Torbjörn E. M. Nordling; Elling W Jacobsen; Rolf Findeisen; KTH; []
    Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; network inference; reverse engineering; variable selection; model selection; feature selection; subset selection; system identification; system theory; network theory; subnetworks; design of experiments; perturbation experiments; gene regulatory networks; biological networks;

    Sammanfattning : In this thesis, inference of biological networks from in vivo data generated by perturbation experiments is considered, i.e. deduction of causal interactions that exist among the observed variables. Knowledge of such regulatory influences is essential in biology. LÄS MER

  7. 5. Perturbed discrete time stochastic models

    Författare :Mikael Petersson; Dmitrii Silvestrov; Ola Hössjer; Nikolaos Limnios; Stockholms universitet; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Renewal equation; Perturbation; Asymptotic expansion; Regenerative process; Risk process; Semi-Markov process; Markov chain; Quasi-stationary distribution; Ruin probability; First hitting time; Solidarity property; Mathematical Statistics; matematisk statistik;

    Sammanfattning : In this thesis, nonlinearly perturbed stochastic models in discrete time are considered. We give algorithms for construction of asymptotic expansions with respect to the perturbation parameter for various quantities of interest. LÄS MER