For this paper: postscript 1 Introduction... Abstract... 3 Systems of coordinates...

2 The collapsing shell 

In a two-dimensional space-time we define:

conformal global coordinates; .

time and distance to an origin ().

Localised massless collapsing shell (, ):

 

Boundary conditions for :

Problem calculate for :


and

Solution:

 

where is a constant (Vendrell (1997a)) (The solution depends actually on the representation of the delta function (eq.3), which is defined here by , where the function is continuous except possibly at .) The functions and are left undetermined for , contrary to the 4-D case (Synge (1957)).