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Title:  Green's functions methods for justifying quasiparticle models 
Author(s):  Craig, Richard Anderson 
Doctoral Committee Chair(s):  Kadanoff, L.P. 
Department / Program:  Physics 
Discipline:  Physics 
Degree:  Ph.D. 
Genre:  Dissertation 
Subject(s):  Green's Function Method
quasiparticle modles many body systems 
Abstract:  The individual particle theory of many body systems was studied starting from a microscopic point of view. A technique which is equivalent to a generalized thermodynamics was used to show that, under the appropriate conditions of temperature and external field, the quasiparticle approach is correct for three very dissimilar systemsi the normal degenerate Fermi system, the metallic electronphonon system, and the polaron. The fact that an approach like this works for such dissimilar systems emphasizes the underlying unity of the quasiparticle models. The concept that the real t~me nonequilibrium selfenergy and the incoherent part of the densitydensity correlation function may be generated as functional derivatives of a generalized thermodynamic potential (~), together with local translational and rotational invariance and Galilean relativity, leads to a transformation from the microscopic particle density variables g«p,m,R,T) to those of the quasiparticle theory n (R,T). ~  p It was shown that, for zero temperature, such a ~ derivability is exact; at low temperature and for slowly varying fields, this ~ derivability is approximately true. This was shown by a procedure which is eqUivalent to an expansion in terms of the real scattering probability for quasiparticles. At low temperature and for slowly varying fields, such real scattering is very improbable and the expansion parameter is small. Perturbation theory was used only to determine the actual size of terms which, on physical grounds are necessarily small. As such, this approach is nonperturbative, depending only on properties of the exact selfenergies and correlation functions. In addition to demonstrating that the quasiparticle models are correct, information on the regions of validity for ~hese models is obtained. .As byproducts of these derivations, microscopic expressions for the parameters of the quasiparticle theory and simple microscopic expressions for the currents in degenerate Fermi systems and the electronphonon system are obtained. 
Issue Date:  1966 
Genre:  Dissertation / Thesis 
Type:  Text 
Language:  English 
URI:  http://hdl.handle.net/2142/23992 
Rights Information:  1966 Richard Anderson Craig 
Date Available in IDEALS:  20110520 
Identifier in Online Catalog:  6170221 
This item appears in the following Collection(s)

Dissertations and Theses  Physics
Dissertations in Physics 
Graduate Dissertations and Theses at Illinois
Graduate Theses and Dissertations at Illinois