Adsorption of a Theta Polymer: Competition Between Mean-Field and Multicritical Behaviour

We analyse the behaviour of a 3d theta polymer in the presence of an attracting wall. We find that the multicritical crossover exponent at the adsorption temperature Ta is the mean-field value φ = 1−νMF = 1/2. However, one only finds a consistent estimate of Ta, if logarithmic corrections are taken into account. This is the first example of numerical data of walks where logarithmic corrections clearly dominate all other possible corrections to scaling. The monomer density near the surface is reduced compared to the mean-field and good-solvent case.