We investigate adsorption of helium in nanoscopic polygonal pores at zero temperature using a finite-range density functional theory. The adsorption potential is computed by means of a technique denoted as the elementary source method. We analyze a rhombic pore with Cs walls, where we show the existence of multiple interfacial configurations at some linear densities, which correspond to metastable states. Shape transitions and hysterectic loops appear in patterns which are richer and more complex than in a cylindrical tube with the same transverse area. DOI: 10.1103/PhysRevB.77.195431 PACS number͑s͒: 68.08.Bc, 68.65.Ϫk, 68.35.Np A widely investigated topic in physics of quantum fluids is the wetting behavior of helium on substrates of different adsorbing powers. For flat surfaces, the latter is determined by the adatom-adsorber interaction; however, the geometrical structure of a matter exposed to the vapor modifies the adsorption strength and the growth of the film.1 A special concern is the filling of pores. Most reported research in this field addresses classical fluids at or close to bulk coexistence and resorts to Monte Carlo, molecular dynamics, and meanfield approaches.2-7 These systems display a rich variety of behaviors, and we expect that this is also true for liquid 4 He in extremely cold quantum regime. In addition to the competition between adhesive ͑fluid-wall͒ and cohesive ͑fluid-fluid͒ forces, which in wetting problems gives rise to phase changes governed by surface effects, pores make room to interplay among finite sizes, geometrical shape of the confinement, and varying dimensionality. Metastable fluid states show up in hysteresis loops in the sorption isotherms, traditionally associated with the onset of capillary condensation ͑CC͒.8 Furthermore, as pointed out in Ref. 3, among the complications arising from almost every model of condensation in pores, there are uncertainties in both the substratefluid and the fluid-fluid interactions. The latter is commonly selected as that in the bulk, while for the adhesive forces, the simplest reduction is the summation of Lennard-Jones pair interactions, 9 which ignores effects that are associated with the polarization and three-body forces.A simple matter unit out of which one may construct polygonal pores of various shapes is the infinite linear wedge. Recently, we presented the theoretical study of condensation of superfluid 4 He in wedges, 10 employing a zero-temperature, finite-range density functional ͑FRDF͒ that has proven helpful to understand a large variety of phenomena in finite systems of liquid helium isotopes and their mixtures.11 The summation employed there to construct the adsorption potential of two semi-infinite walls meeting at a corner can be improved by a newly reported method 12 that gives the potential of a substrate of arbitrary shape, provided that the ab initio adsorption field for the semi-infinite material with a planar surface is known. This method consists of solving an inverse problem to determine the elementary source ...