SVIBOR - Project code: 1-03-103

MINISTRY OF SCIENCE AND TECHNOLOGY

Strossmayerov trg 4, HR - 10000 ZAGREB
tel.: +385 1 459 44 44, fax: +385 1 459 44 69
E-mail: ured@znanost.hr

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Project code: 1-03-103


THEORY OF CRITICAL PHENOMENA


Main researcher: UZELAC, KATARINA (51256)


Assistants
Type of research: basic
Duration from: 01/01/91. to 12/31/95.
Papers on project (total): 33
Papers on project quoted in Current Contents: 28
Institution name: Institut za fiziku, Zagreb (35)
Communication
Phone: 385-1-271-211, ku†. 237
Fax: 385-1-421-156
E-mail: uzelac@athena.ifs.hr
Summary: Investigations involve static and dynamic phase transitions, as well as critical phenomena related to irreversible processes studied by application of scaling, renormalisation group and related methods, including numerical simulations. In particular are considered the critical behaviour of low-dimensional classical models with long-range interactions, quantum phase transitions in spin and fermion models on lattice, structural phase transitions arising in description of high Tc superconductivity. Investigations also include models related to aggregation phenomena and equilibrium phase transitions within disordered or fractal structures.

Keywords: critical phenomena, phase transitions, critical exponents, scaling, renormalisation group, supraconductivity, crossover, Ising model, Potts model, Yang-Lee edge singularity

Research goals: The aim of present investigations is to obtain better insight into mechanisms of phase transitions for models of classical spins, as well as for quantum phase transitions considered here within context of presently relevant problems of solid state theory (high Tc superconductivity, Peierls instability,..). As it concerns classical spins, the intention was to apply the new method for studying systems with long range interactions to series of models, in particular Yang-Lee edge singularity, Potts model with long-range interactions. The choice of Potts model, where by changing of parameters several different regimes of critical behaviour can be covered, is convenient to obtain better general description, as well as to find analogies with similar transitions in other systems. Phase transitions within porous materials have been studied in order to explain new transitions and other new features observed in series of recent experiments on Helium and liquid crystals within porous glasses. Problem is also interesting within context of theoretical studies of phase transitions in presence of strongly correlated disorder. The part of investigations involving quantum fluctuations have provided better understanding of experimental results on concrete systems. Some mutually contradictory experimental findings in high-temperature superconducting materials can be understood by using "slave boson method", an approach convenient to study strongly correlated fermionic systems. Numerical simulations of small electron-phonon systems have provided a better understanding of the Raman and infra-red spectra, ESR measurements as well as EXAFS data for low dimensional systems.

COOPERATION - PROJECTS


  1. Name of project: Phenomenes critiques et transitions de phase dans les systemes quantiques (hrv.: Kritične pojave i fazni prijelazi u kvantnim sistemima)
    Name of institution: Laboratoire de Physique des Solides, Universite Paris-Sud
    City: 91405 - Orsay, Francuska

COOPERATION - INSTITUTIONS


  1. Name of institution: Laboratoire de Physique des Solides, Universite Paris-Sud
    Type of institution: University/Faculty
    Type of cooperation: Joint project
    City: 91405 - Orsay, Francuska

  2. Name of institution: Physique des materiaux vitreux, Universite de Montpellier II
    Type of institution: University/Faculty
    Type of cooperation: Joint publishing of scientific papers
    City: 34095 - Montpellier, Francuska
Other information about the project.
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