  The Jackiw-Teitelboim gravity with the matter degrees of freedom is
considered. The classical model is exactly solvable and its solutions describe
non-trivial gravitational scattering of matter wave-packets. For huge amount of
the solutions the scattering space-times are free of curvature singularities.
However, the quantum corrections to the field equations inevitably cause the
formation of (thunderbolt) curvature singularities, vanishing only in the limit
$\hbar\to 0$. The singularities cut the space-time and disallow propagation to
the future.The model is inspired by the dimensional reduction of 4-d pure
Einstein gravity, restricted to the space-times with two commuting space-like
Killing vectors. The matter degrees of freedom also stem from the 4-d ansatz.
The measures for the continual integrations are judiciously chosen and one loop
contributions (including the graviton and the dilaton ones) are evaluated. For
the number of the matter fields $N=24$ we obtain even the exact effective
action, applying the DDK-procedure. The effective action is nonlocal, but the
semiclassical equations can be solved by using some theory of the Hankel
transformations.
