Formation of caustics in Dirac-Born-Infeld type scalar field systems

We investigate the formation of caustics in the Dirac-Born-Infeld type scalar field systems for generic classes of potentials, viz., massive rolling scalar with potential, V(ϕ)=V₀e^±(1/2)M2ϕ2 and inverse power-law potentials with V(ϕ)=V₀/ϕⁿ, 0<n<2. It is found that in the case of exponentially decreasing rolling massive scalar field potential, there are multivalued regions and regions of likely to be caustics in the field configuration. However there are no caustics in the case of exponentially increasing potential. We show that the formation of caustics is inevitable for the inverse power-law potentials under consideration in Minkowski space time whereas caustics do not form in this case in the Friedmann-Robertson-Walker Universe.