In this paper we introduce a new deformation argument, in which C 0 -group action and a new type of Palais-Smale condition PSP play important roles. This type of deformation results are studied in [17,21] and has many different applications [10,11,17,21] et al. Typically it can be applied to nonlinear scalar field equations. We give a survey in an abstract functional setting. We also present another application to nonlinear elliptic problems in strip-like domains. Under conditions related to [5,6], we show the existence of infinitely many solutions. This extends the results in [8].