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Pethick, C.J. Pines, David Coffey, Dermot 2011-06-02T17:15:46Z 2011-06-02T17:15:46Z 10000-01-01 1986 In this thesis I study two separate topics in many-body physics. In the first part I consider many-body effects in the thermodynamic properties of Fermi liquids and of the electron-phonon system. Using normal liquid 3He as an example, I show that the T3lnT corrections due to spin fluctuations account for the finite temperature corrections to the leading term in the specific heat. I also calculate and compare the statistical and the dynamical quasiparticle spectra and show that differences between them partially account for the discrepancy between the present and previous results. Spin fluctuation parameters determined from fits to specific heat of UPt3 and UA12 are examined and applicability of simple spin-fluctuation models to these systems is discussed. In addition I consider the T3lnT contributions to the specific heat of metals due to the electron-phonon coupling and show how they may be viewed as being analogous to those from spin fluctuations. In the second part of the thesis I review the application of polarization potential theory to the description of the excitations of liquid 4He at low temperature and I use recent experimental results to determine the parameters in the theory. I calculate the dispersion curve in the absence of dynamic mode-mode coupling and discuss the results. Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-06-02T17:15:46Z No. of bitstreams: 1 1986_coffey.pdf: 8025403 bytes, checksum: caf51f4345237dd92b2a76cc6f2d68fd (MD5) Made available in DSpace on 2011-06-02T17:15:46Z (GMT). No. of bitstreams: 1 1986_coffey.pdf: 8025403 bytes, checksum: caf51f4345237dd92b2a76cc6f2d68fd (MD5) Previous issue date: 1986 Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Carolyn Mead (cmead2@illinois.edu) on 2011-06-02T17:15:46Z Item is restricted indefinitely. Restriction data tranferred 2014-07-01T11:14:47-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: Thesis Thesis U of I Only 1001002 http://hdl.handle.net/2142/25227 en 1986 Dermot Coffey many-body thermodynamics Fermi liquids electron-phonon system liquid 4He quasiparticle spectra Many-body effects in the thermodynamic properites of Fermi liquids and the electron-phonon system and in the excitation spectrum of liquid 4HE Dissertation / Thesis text Physics Physics University of Illinois at Urbana-Champaign Dissertation Ph.D.