  The Rouse model has recently been modified to take into account the excluded
volume interactions that exist between various parts of a polymer chain by
incorporating a narrow Gaussian repulsive potential between pairs of beads on
the Rouse chain (cond-mat/0002448). The narrow Gaussian potential is
characterized by two parameters: z* - which accounts for the strength of the
interaction, and d* - which accounts for the extent of the interaction. In the
limit of d* going to zero, the narrow Gaussian potential tends to the more
commonly used delta-function repulsive potential. The influence of the
parameter d*, in the limit of infinite chain length, on equilibrium and linear
viscoelastic properties, and on universal ratios involving these properties, is
examined here. A renormalization group calculation of the end-to-end vector
suggests that the value chosen for the variable d* will not affect critical
exponents, or universal ratios. A similar trend is also observed for results
obtained with an approximate solution, which is based on the assumption that
the non-equilibrium configurational distribution function is Gaussian.
