High-speed cylindrical collapse of perfect fluid

The gravitational collapse of a cylindrically distributed perfect fluid is studied. We assume that the collapsing speed of the fluid is very large and investigate such a situation using recently proposed high-speed approximation scheme. We show that if the value of the pressure divided by the energy density is bounded below by some positive value, the high-speed collapse is necessarily decelerated by pressure repulsion so significantly that this approximation scheme becomes inapplicable. However, even in the case of a mono-atomic ideal gas, which is a typical example of the bounded case, an arbitrarily large tidal force for freely falling observers can be realized before the high-speed approximation breaks down if the initial collapsing velocity is set to a very large value. By contrast, in case that the equation of state is sufficiently soft, we find that the high-speed collapse is maintained until a spacetime singularity forms.