Sökning: "quantum vacuum"

Visar resultat 16 - 20 av 49 avhandlingar innehållade orden quantum vacuum.

1. 16. Non-Perturbative Quantum Field Theory in Extreme Environments

   Författare :Per Liljenberg; Chalmers tekniska högskola; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; pair production; Bose-Einstein condensation; functional representation; Schwinger model; external field; boson stars; temperature; magnetisation;

   Sammanfattning : The aim of this thesis is to describe some physical systems which can be treated by non-perturbative methods in quantum field theory. In the thesis we study systems described by quadratic Hamiltonians, possibly extended with an external electromagnetic field and/or with a thermal heat bath. LÄS MER

3. 17. Theoretical modeling of scanning tunneling microscopy

   Författare :Alexander Gustafsson; Magnus Paulsson; Jorge Iribas Cerdá; Linnéuniversitetet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Scanning tunneling microscopy; Computational models; Quantum tunneling; Green s functions; Density functional theory; Condensed Matter Physics; Kondenserade materians fysik;

   Sammanfattning : The main body of this thesis describes how to calculate scanning tunneling microscopy (STM) images from first-principles methods. The theory is based on localized orbital density functional theory (DFT), whose limitations for large-vacuum STM models are resolved by propagating localized-basis wave functions close to the surface into the vacuum region in real space. LÄS MER

4. 18. Electron Transport in Semiconductor Nanowires

   Författare :Mikael Björk; Fasta tillståndets fysik; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; heterostructures; single electron transistors; resonant tunneling; quantum dots; weak antilocalization; Halvledarfysik; field effect transistors; Semiconductory physics; Fysicumarkivet A:2004:Björk; Low-dimensional structures; nanowires; chemical beam epitaxy;

   Sammanfattning : In this thesis, semiconductor nanowires are studied from the point of view of growth and electrical properties. The growth of nanowires is done by chemical beam epitaxy (CBE), an ultra-high vacuum technique allowing a precise control of precursor deposition and low growth rates. LÄS MER

5. 19. Tunneling Based Electronic Devices

   Författare :Erik Lind; Institutionen för elektro- och informationsteknik; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; SiGe; Esaki Diodes; classical mechanics; quantum mechanics; relativity; termodynamik; relativitet; kvantmekanik; statistisk fysik; Matematisk och allmän teoretisk fysik; thermodynamics; gravitation; statistical physics; GaAs; Mathematical and general theoretical physics; Resonant Tunneling Permeable Base Transistors; Resonant Tunneling Diodes; klassisk mekanik; Fysicumarkivet A:2004:Lind;

   Sammanfattning : This thesis concerns different kinds of tunneling based devices all showing negative differential resistance. The thesis is divided in three parts, resonant tunneling transistors, Esaki diodes and coupled zero dimensional systems. LÄS MER

7. 20. Structure and spectroscopy of bio- and nano-materials from first-principles simulations

   Författare :Weijie Hua; Yi LUO; Mauro Stener; KTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; soft x-ray spectroscopy; bio- and nano-materials; first-principles simulation; host-guest interaction; generalized energy-based fragmentation; Quantum chemistry; Kvantkemi; Spectroscopy; Spektroskopi; SRA - Molecular Bioscience; SRA - Molekylär biovetenskap;

   Sammanfattning : This thesis is devoted to first-principles simulations of bio- and nano-materials,focusing on various soft x-ray spectra, ground-state energies and structures of isolated largemolecules, bulk materials, and small molecules in ambient solutions. K-edge near-edge x-ray absorption fine structure (NEXAFS) spectra, x-ray emission spectra, andresonant inelastic x-ray scattering spectra of DNA duplexes have been studied by means oftheoretical calculations at the density functional theory level. LÄS MER