The critical behaviour of a dilute spin-S Bose gas in a magnetic field is investigated with the help of the renormalization group method. A complete set of critical exponents is given both at constant pressure and constant density. The magnetic properties are also discussed.
We applied the Renormalization Group method at finite temperature to reconsider the two-dimensional dilute Bose gas. The general flow equations are obtained for the case of arbitrary dimensions, and by considering the two-dimensional limit, we estimate the value of the critical temperature, coherence length and specific heat. The value of the critical temperature is in agreement with previous calculations performed using the t-matrix method. The coherence length and the specific heat present a non-universal behavior, a logarithmic temperature dependence in the critical region being identified.
A homogeneous non-relativistic Bose gas is investigated at finite temperature using renormalization group methods. The phase transition is shown to be second order and the effective chemical potential and the effective quartic coupling vanish at the critical temperature. We obtain the critical exponent ν=0.73 at leading order in the derivative expansion.
The thermodynamic properties of a Bose gas of particles with nonzero spin and magnetic moment in states with and without a Bose-Einstein condensate are studied as a function of the external magnetic field. It is shown that there exists a temperature interval where a transition into a state with a Bose-Einstein condensate occurs in a Bose gas with constant temperature and particle number density when the magnetic field is increasing and reaches a critical magnitude. The temperature and magnetic field derivatives of the specific heat at constant volume and the magnetic susceptibility undergo a jump at such a transition.
We study the d -dimensional Bose gas at finite temperature using the renormalization-group method. The flow-equations and the free energy are obtained for dimension d , and the cases d < 2 and d = 2 have been analysed in the limit of low and high temperatures. The critical temperature, the coherence length and the specific heat of a two-dimensional Bose gas are obtained using a regular solution for the coupling constant which is obtained from the scaling equations. The relevance of the dilute Bose gas for recent experimental results is also discussed.
We study the three-dimensional atomic Bose gas using renormalization group techniques. Using our knowledge of the microscopic details of the interatomic interaction, we determine the correct initial values of our renormalization group equations and thus obtain also information on nonuniversal properties. As a result, we can predict, for instance, the critical temperature of the gas and the superfluid and condensate density of the Bose-Einstein condensed phase in the regime na${\mathrm{\ensuremath{\Lambda}}}_{\mathit{th}}^{2}$\ensuremath{\ll}1, where the average interaction energy is small compared to the average kinetic energy. \textcopyright{} 1996 The American Physical Society.