“…It is possible to consider similar questions with some other operators (see, for example, [4] for a 2m-th order operator in bounded non-rectangular domains). Whereas second-order parabolic equations in bounded non-cylindrical domains are well studied (see for instance [1,6,9,12,14,15,18,19,20,23] and the references therein), the literature concerning unbounded non-cylindrical domains does not seem to be very rich. The regularity of the heat equation solution in a non-smooth and unbounded domain (in the t direction) is obtained in [21] and [22] by using two different approaches.…”