The affine maximal equation is the Euler-Lagrange equation of the affine area functional for a locally uniformly convex
graph. For a smooth function on an open domain in
with positive definite Hessian,
put
and
.
The equation is
The corresponding functional is for compactly
supported variations. Every quadratic polynomial
with positive definite Hessian
solves the equation, since
is constant. The affine
Bernstein conjecture asks when complete solutions must be quadratic.