SVIBOR - Project code: 1-03-170

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Project code: 1-03-170


RESEARCH IN MICROSCOPIC THEORY OF QUANTUM FLUIDS


Main researcher: KILIĆ, SREĆKO (20873)


Assistants
Type of research: basic
Duration from: 01/01/91. to 12/31/93.
Papers on project (total): 0
Institution name: Fakultet prirodoslovno matematičkih znanosti i odgojnih područja, Split (177)
Department/Institute: Department of Physics
Address: Nikole Tesle 12, 58000 Split, Croatia
City: 21000 - Split, Croatia
Communication
E-mail: kilic@mapmf.pmfst.hr
Phone: 385 (0)21 587133
Fax: 385 (0)21 362431
Summary: We considered an electron gas at high density. The essential part of the ground state energy is given by the Gell-Mann - Brueckner relation. The corrections were calculated including non ring-diagrams. We calculated ground state energy by including a new class of diagrams and derived the next coeficient in series proportional to small parameter. Pines and coworkers have found the interaction energy between two quasiparticles in helium 4 using the pseudopotential method. The main feature of this interaction is a change of sign when the density increases. We tried to show that this behaviour is a general feature of all boson systems with short range repulsive potential and long range attracive potential. We showed that Bogoliubov approximation was not enough good to reproduce this anticipation. Variational ansatz in quantum mechanics could be derived for lower bound as well. We considered quite generally a fermion system and we showed a general theorem for lower bound on energy which includes any order of multiplicity of correlations among particles.

Keywords: Quantum fluids, liquid helium 3 and 4, quasiparticles, variational ansatz, bosons, fermions, multiparticle correlations, anisotropic liquid, fermion gas, electron gas.

Research goals: Having in mind the structure of the perturbation theory weintended to derive a general expression for the ground state energy of a fermionsystem, which would include some classes of non-ring diagrams and considered a new typeof excitations in these systems. There is a need to derive a microscopic theory from the firstprinciples for the interaction between quasiparticles in boson systems andour goal was to obtain this energy using the perturbation theory. We expected to study, on the same basis, the other properties, as for instance pressure dependence. We intended to calculate the ground state energy and elementaryexcitation spectrum of anysotropic fermion systems; then it would be applied toliquid helim 3. Performing a general theorem for lower bound of the ground stateenergy of fermion system was also our goal. We planed to include in it anyorder of the correlation. All goals, except the one relating to anysotropic liquid, were reched.

COOPERATION - PROJECTS


  1. Name of project: Application of perturbation techniques beyond the Feenberg one to strongly correlated electron systems
    Name of institution: Lehrstuhl fuer Theoretische Physik I, Universitaet Dortmund
    City: D-44221 - Dortmund, Germany

COOPERATION - INSTITUTIONS


  1. Name of institution: Fakultet elektrotehnike, strojarstva i brodogradnje
    Type of institution: University/Faculty
    Type of cooperation: Joint publishing of scientific papers
    City: 21000 - Split, Croatia

  2. Name of institution: Građevinski fakultet
    Type of institution: University/Faculty
    Type of cooperation: Joint publishing of scientific papers
    City: 51000 - Rijeka, Croatia

  3. Name of institution: School of Physics and Astronomy, University of Minnesota
    Type of institution: University/Faculty
    Type of cooperation: Joint publishing of scientific papers
    City: Minneapolis, U.S.A.

  4. Name of institution: Lehrstuhl fuer Theoretische Physik I, Universitaet Dortmund
    Type of institution: University/Faculty
    Type of cooperation: Joint project
    City: D-44221 - Dortmund, Germany
Other information about the project.
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