Exact Functional Renormalization Group for Wetting Transitions in 1 + 1 Dimensions.

PACS. 68.45- Solid-fluid interface processes. PACS. 64.60- General studies of phase transitions. Abstract.- Using an exact functional renormalization group (RG), we study wetting transitions in d = 1 + 1 dimensions. This RG acts in the function space of the interaction potentials for two interfaces. The RG flow exhibits i) a whole line of fixed points and ii), a separatrix which represents an analytic continuation of the fixed-point line. Numerical and analytical work shows that the line of fixed points almost forms a closed loop in function space. The separatrix, on the other hand, describes a subregime where the wetting transitions are fiist-order but have unusual scaling properties. A generalization of the RG indicates that these unusual transitions are replaced by usual first-order transitions in d # 1 + 1. Functional renormalization group (RG) methods were originally developed in the context of bulk critical phenomena, i.e. critical phenomena arising at phase transitions in bulk systems. The first such method was nonperturbative and led to an approximate functional RG[1] which served, however, as a starting point for perturbative but systematic RG methods [2]. For bulk critical phenomena, exact functional RG transformations have als