DYNAMICS OF A SPHERICALLY SYMMETRICAL SCALAR SHELL - ART. NO. 083506

In this work we analyze the motion of a thin shell composed of a scala r field. We study the equations of motion resulting from the matching conditions of the two surrounding vacuum spacetimes which are describe d by the Schwarzschild metric. It is shown that there exist numerical solutions which describe shells which collapse, expand, and oscillate. The conditions for gravitational collapse are obtained by analyzing c ertain effective potentials. In particular, for a massless scalar fiel d we show that the collapse occurs only if the parameters determining the gravitational mass and the pressure of the shell are proportional. The case of a static configuration is also investigated. [S0556-2821( 98)05118-2].