“…It is widely known that the Ambrosetti–Rabinowitz condition (
for short) in Ambrosetti and Rabinowitz [
9], that is, there exist
and
, such that
is an important condition to ensure the boundedness of the Palais–Smale (PS) sequence of an energy functional and crucial in the application of the critical point theory. This is why, in the last few years, some authors of previous works [
10–15] have tried to get rid of the
condition.…”