We compare the statistical properties of bright galaxies found in two different models of galaxy formation — the semi-analytic model of Cole et al. (1999) and the smoothed particle hydrodynamics (SPH) simulations of Pearce et al. (1999) — in cold dark matter universes. These two techniques model gas processes very differently: by approximate, analytic methods in the case of semi-analytic models...

We investigate relativistic flows after a shock wave generated in a star arrives at the surface. First, the sphericity effect is involved through a successive approximation procedure by adding correction terms to an already known self-similar solution in the ultra-relativistic limit assuming the plane parallel geometry. It is found that the lowest order correction terms are of the order of (a/R...

Many similarity solutions have been found for the equations of one-dimensional (1-D) hydrodynamics. These special combinations of variables allow the partial differential equations to be reduced to ordinary differential equations, which must then be solved to determine the physical solutions. Usually, these reduced ordinary differential equations are solved numerically. In some cases it is poss...

We model the overall shape of an accretion disc in a semi-detached binary system in which mass is transfered on to a spinning black hole the spin axis of which is misaligned with the orbital rotation axis. We assume the disc is in a steady state. Its outer regions are subject to differential precession caused by tidal torques of the companion star. These tend to align the outer parts of the dis...