Sökning: "perturbation theory."

Visar resultat 21 - 25 av 148 avhandlingar innehållade orden perturbation theory..

1. 21. Towards a relativistically covariant many-body perturbation theory - With numerical implementation to helium-like ions

   Författare :Daniel Hedendahl; Göteborgs universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; many-body perturbation theory; bound state QED; helium-like ions; Green s operator; covariant evolution operator; combined effects of QED and correlation; atomic structure calculations;

   Sammanfattning : The experimental results for simple atomic systems have become more and more accurate and in order to keep up with the experimental achievements the theoretical procedures have to be refined. Recent accurate experimental results obtained for helium-like ions in the low- and moderate-Z regions proclaim the importance of theoretical calculations that combines relativistic, QED and electron correlation effects. LÄS MER

3. 22. Yang-Mills Theory in Gauge-Invariant Variables and Geometric Formulation of Quantum Field Theories

   Författare :Sergey Slizovskiy; Antti Niemi; Andrey Losev; Andrey Marshakov; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Yang-Mills theory; spin-charge separation; Kaluza-Klein theory; branes; curved beta-gamma systems; Mathematical physics; Matematisk fysik; Theoretical Physics; Teoretisk fysik;

   Sammanfattning : In Part I we are dealing with effective description of Yang-Mills theories based on gauge-invarint variables. For pure Yang-Mills we study the spin-charge separation varibles. The dynamics in these variables resembles the Skyrme-Faddeev model. LÄS MER

4. 23. Perturbed Renewal Equations with Non-Polynomial Perturbations

   Författare :Ying Ni; Dmitrii Silvestrov; Anatoliy Malyarenko; Yuri Belyaev; Mälardalens högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Renewal equation; perturbed renewal equation; non-polynomial perturbation; exponential asymptotic expansion; risk process; ruin probability; Mathematical statistics; Matematisk statistik; Mathematics Applied Mathematics; matematik tillämpad matematik;

   Sammanfattning : This thesis deals with a model of nonlinearly perturbed continuous-time renewal equation with nonpolynomial perturbations. The characteristics, namely the defect and moments, of the distribution function generating the renewal equation are assumed to have expansions with respect to a non-polynomial asymptotic scale: $\{\varphi_{\nn} (\varepsilon) =\varepsilon^{\nn \cdot \w}, \nn \in \mathbf{N}_0^k\}$  as $\varepsilon \to 0$, where $\mathbf{N}_0$ is the set of non-negative integers, $\mathbf{N}_0^k \equiv \mathbf{N}_0 \times \cdots \times \mathbf{N}_0, 1\leq k . LÄS MER

5. 24. Isospin Breaking in Kaon Decays to Pions

   Författare :Fredrik Borg; Teoretisk partikelfysik - Geonomgår omorganisation; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Elementary particle physics; termodynamik; statistisk fysik; gravitation; relativitet; kvantmekanik; thermodynamics; Matematisk och allmän teoretisk fysik; Pseudo-scalar meson; Isospin Breaking; Chiral Perturbation Theory; Mathematical and general theoretical physics; classical mechanics; quantum mechanics; relativity; statistical physics; Weak Interaction; Strong Interaction; kvantfältteori; High energy interactions; Kärnfysik; Nuclear physics; klassisk mekanik; quantum field theory; cosmic rays; Kosmisk strålning; högenergi; Elementarpartikelfysik;

   Sammanfattning : The five different K -> 3 Pi and the three K -> 2 Pi decays are calculated in Chiral Perturbation Theory. The calculation is done using different approximations, to study whether this changes the result significantly. First the isospin approximation is used. Discrepancies are then found between theory and experiment. LÄS MER

7. 25. Modeling of intra- and intermolecular potentials

   Författare :Stevica Brdarski; Beräkningskemi; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Theoretical chemistry; N-formylglycinamide; formamide; water dimer; quantum chemistry; molecular dynamics simulations; repulsion modeling; perturbation theory; NEMO; molecular interactions; Teoretisk kemi; kvantkemi;

   Sammanfattning : Modeling of interactions between molecules is investigated by theoretical means within the NEMO model. The model is based on a partitioning of the interaction energy at the Hartree-Fock level into first- and second-order perturbation theory. The interaction energy is given as a sum of electrostatic, induction, repulsion, and dispersion energies. LÄS MER