Consider a continuous function on a metric space. In the presence of linking between a compact pair and a closed set, depending on the different behaviors of the function on the linking sets, we establish minimax results guaranteeing existence of Palais-Smale sequences or providing gradient estimates. Our approach relies on deformation techniques.
"Minimax Results with Respect to Different Altitudes in the Situation of Linking." Abstr. Appl. Anal. 2013 (SI61) 1 - 6, 2013. https://doi.org/10.1155/2013/781746