Critical gravitational collapse of a massive complex scalar field

Abstract

We study the critical collapse of a massive complex scalar field coupled minimally to gravity. Taking as initial data a simple gaussian pulse with a shape similar to the harmonic ansatz for boson stars, we obtain critical collapse of type type I and II when varying the gaussian width $\sigma$. For $\sigma \leq 0.5$ we find collapse of type II with a critical exponent $\gamma=0.38\pm0.01$ and an echoing period $\Delta=3.4\pm0.1$. These values are very similar to the known results for a real massless scalar field. On the other hand, for $\sigma \geq 2.5$ we obtain collapse of type I. In this case we find that the critical solutions turn out to be an unstable boson stars in the ground state: all the data obtained from our simulations can be contrasted with the characteristic values for unstable boson stars and their corresponding Lyapunov exponents.