  It is known that a bounded solution of the heat equation in a half-space
which becomes zero at some time must be identically zero, even though no
assumptions are made on the boundary values of the solutions. In a recent
example, Luis Escauriaza showed that this statement fails if the half-space is
replaced by cones with opening angle smaller than 90 degrees. Here we show the
result remains true for cones with opening angle larger than 110 degrees. The
proof covers heat equations having lower-order terms with bounded measurable
coefficients.
