Search for dissertations about: "density-matrix"

Showing result 1 - 5 of 49 swedish dissertations containing the word density-matrix.

2. 1. The density-matrix formalism for description of step-wise laser-excitations of atoms and molecules in high-collisional media

   Author : Peter Ljungberg; Chalmers tekniska högskola; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; density-matrix; pulsed lasers; anomalous saturation curved; laser spectroscopy; stark split; degenerate states; rate-equations;

   Abstract : .... READ MORE

4. 2. Strongly Correlated Models in One Dimension from a Density Matrix Renormalization Group Perspective

   Author : Stefan Rommer; Chalmers tekniska högskola; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; matrix product states; impurities; density matrix renormalization group; Heisenberg model; spin chain; DMRG;

   Abstract : The density matrix renormalization group (DMRG) is a numerical method for studying low dimensional strongly correlated models. The study of these models is one of the most active areas of condensed matter physics today and has been spurred not only by the discovery of high temperature superconductivity but also by experiments on new compounds. READ MORE

5. 3. Efficient Density Matrix Methods for Large Scale Electronic Structure Calculations

   Author : Anastasia Kruchinina; Emanuel H. Rubensson; Elias Rudberg; David Bowler; Uppsala universitet; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; electronic structure; linear scaling; density matrix; density functional theory; Hartree-Fock; recursive polynomial expansion; density matrix purification; eigenvectors; molecular orbitals; stopping criteria; inverse factorization; matrix sparsity; parallelization; Scientific Computing; Beräkningsvetenskap;

   Abstract : Efficient and accurate methods for computing the density matrix are necessary to be able to perform large scale electronic structure calculations. For sufficiently sparse matrices, the computational cost of recursive polynomial expansions to construct the density matrix scales linearly with increasing system size. READ MORE

6. 4. Some Aspects of Non-Perturbative Quantum Field Theory

   Author : Joakim Hallin; Chalmers tekniska högskola; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES; Yang-Mills; QED; pair production; density matrix; external field; Schwinger model; gauge invariant; functional representation;

   Abstract : The aim of this thesis is to describe some different ways in which non-perturbative methods enter in quantum field theory. In the thesis such methods enter in 1+1-dimensional theories: various Yang-Mills theories and electrodynamics. It also enters when treating charged bosons or fermions interacting with an external, classical field. READ MORE

7. 5. Density Matrix Renormalization Group approach to anisotropic 3-dimensional bosons

   Author : Gunnar Bollmark; Adrian Kantian; Salvatore Manmana; Uppsala universitet; []
   Keywords : NATURVETENSKAP; NATURAL SCIENCES;

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