Using some observations and some mean-field approximations, we develop a mean-field cage theory for the freezing of hard-sphere fluids with υf≥ad and obtain the freezing densities as functions of the closest-packing densities and the spatial densities, which are in good agreement with the experimental and simulation results.

We use the real-space renormalization-group approach to calculate the fractal dimension of diffusion-limited aggregation for a alttice with an arbitrary Euclidean dimension d. The results obtained are in good agreement with numerical numerical results. We prove that D → d-1 as d → ∞

A much simpler method is proposed for the evaluation of the exact finite-temperature particle and energy densities for noninteracting Bose and Fermi gases in d-dimensional anisotropic harmonic traps. For the Bose gas in the whole range of temperature, the exact results are obtained. For the Fermi gas with chemical potential less than the single-particle ground-state energy, the exact results are obtained.

Based on Meakin' s simulation results [Phys. Rev. A 34, 710 (1986); 35, 2234 (1987)], we use the bino-mial distribution to discuss the growth probability for the screened-growth model and develop a formula of the generalized dimensions. The results from this model are in good agreement with those from the simulations.

The Yang-Lee circle theorem is extended to an ideal pseudospin-1/2 Bose gas in an external magnetic field. It is found that the zeros of the canonical partition function are located on the unit circle in the complex activity plane if the temperature is above the critical temperature of ideal Bose-Einstein condensation. No zeros exist if the temperature is below the critical temperature.