Special cases:
, fold catastrophe;
, cusp catastrophe;
, swallowtail catastrophe.
(elliptic umbilic).
(hyperbolic umbilic).
with the contour passing to the lower right of
.
with the contour passing to the upper right of
.
is related to the Airy function (§9.2):
is the Pearcey integral (Pearcey (1946)):
(Other notations also appear in the literature.)
Addendum: For further special cases see §36.2(iv)
(rotation by
in
plane).

Here the functions
and
are the complex conjugates of the functions
and
, respectively.