On the formation of a quasi-stationary twisted disc after a tidal
  disruption event
  We investigate misaligned accretion discs formed after tidal disruption
events that occur when a star encounters a supermassive black hole. We employ
the linear theory of warped accretion discs to find the shape of a disc for
which the stream arising from the disrupted star provides a source of angular
momentum that is misaligned with that of the black hole. For quasi-steady
configurations we find that when the warp diffusion or propagation time is
large compared to the local mass accretion time and/or the natural disc
alignment radius is small, misalignment is favoured. These results have been
verified using SPH simulations. We also simulated 1D model discs including gas
and radiation pressure. As accretion rates initially exceed the Eddington limit
the disc is initially advection dominated. Assuming the $\alpha$ model for the
disc, where it can be thermally unstable it subsequently undergoes cyclic
transitions between high and low states. During these transitions the aspect
ratio varies from $\sim 1$ to $\sim 10^{-3}$ which is reflected in changes in
the degree of disc misalignment at the stream impact location. For maximal
black hole rotation and sufficiently large values of viscosity parameter
$\alpha > \sim 0.01-0.1$ the ratio of the disc inclination to that of the
initial stellar orbit is estimated to be $0.1-0.2$ in the advection dominated
state, while reaching of order unity in the low state. Misalignment descreases
with decrease of $\alpha$, but increases as the black hole rotation parameter
decreases. Thus, it is always significant when the latter is small.
