A. Ishibashi et A. Hosoya, Who's afraid of naked singularities? Probing timelike singularities with finite energy waves - art. no. 104028, PHYS REV D, 6010(10), 1999, pp. 4028
To probe naked spacetime singularities with waves rather than with particle
s we study the well posedness of initial value problems for test scalar fie
lds with finite energy so that the natural function space of initial data i
s the Sobolev space. In the case of static and conformally static spacetime
s we examine the essential self-adjointness of the time translation operato
r in the wave equation defined in the Hilbert space. For some spacetimes th
e classical singularity becomes regular if probed with waves while stronger
classical singularities remain singular. If the spacetime is regular when
probed with waves we may say that the spacetime is ''globally hyperbolic.''
[S0556-2821(99)00620-7].