  Dissolved ions can alter the local permittivity of water, nevertheless most
theories and simulations ignore this fact. We present a novel algorithm for
treating spatial and temporal variations in the permittivity and use it to
measure the equivalent conductivity of a salt-free polyelectrolyte solution.
Our new approach quantitatively reproduces experimental results unlike
simulations with a constant permittivity that even qualitatively fail to
describe the data. We can relate this success to a change in the ion
distribution close to the polymer due to the built-up of a permittivity
gradient.
