Sökning: "Many-body perturbation theory"

Visar resultat 1 - 5 av 17 avhandlingar innehållade orden Many-body perturbation theory.

1. 1. Time-Dependent Many-Body Perturbation Theory: Possibilities and Limitations

   Författare :Marc Puig von Friesen; Matematisk fysik; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Many-body perturbation theory; Correlation functions; Hubbard model; Non-equilibrium Green s functions; Fysicumarkivet A:2011:Puig von Friesen;

   Sammanfattning : This dissertation investigates the possibilities and limitations of time-dependent many-body perturbation theory by studying small Hubbard clusters for which the exact solution is available. The first part of the thesis is comprised of a short introduction to the concepts and methodologies used. LÄS MER

3. 2. Many-Body effects in Semiconductor Nanostructures

   Författare :Carl-Johan Wesslén; Eva Lindroth; Morten Førre; Stockholms universitet; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; NATURVETENSKAP; NATURAL SCIENCES; coupled cluster; nanostructure; quantum dot; quantum ring; concentric quantum ring; many body pertubation theory; fysik; Physics;

   Sammanfattning : Low dimensional semiconductor structures are modeled using techniques from the field of many-body atomic physics. B-splines are used to create a one-particle basis, used to solve the more complex many-body problems. LÄS MER

4. 3. 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

5. 4. On the role of the electron-electron interaction in two-dimensional quantum dots and rings

   Författare :Erik Waltersson; Eva Lindroth; Stephanie Reimann; Stockholms universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; quantum dot; quantum ring; quantum dot molecule; electronic structure; two-dimensional; many-body physics; many-body perturbation theory; coupled cluster; coupled cluster singles and doubles; quantum logical gates; quantum computing; quantum control; quantum control algorithm; Electronic structure; Elektronstruktur; fysik; Physics;

   Sammanfattning : Many-Body Perturbation Theory is put to test as a method for reliable calculations of the electron-electron interaction in two-dimensional quantum dots. We show that second order correlation gives qualitative agreement with experiments on a level which was not found within the Hartree-Fock description. LÄS MER

7. 5. Theoretical Developments for the Real-Time Description and Control of Nanoscale Systems

   Författare :Miroslav Hopjan; Matematisk fysik; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Green’s Function; DFT; TDDFT; Hubbard Model; Many-Body Perturbation Theory; Strongly Correlated Systems; Quantum Transport; Disorder; Ehrenfest Dynamics; Electronic Friction; Exact Diagonalization; Periodic Anderson Model; Fysicumarkivet A:2018:Hopjan;

   Sammanfattning : In this thesis we focus on improvements of the description of the electron-electron correlation effects in nonequilibrium nanosystems. We mainly focus on developments of two nonequilibrium methods, namely the formalism of Nonequilibrium Green’s Function and Time Dependent Density Functional Theory and we explore the possibility to improve existing approximations in these theories. LÄS MER