The simplest model consistent with a Gaussian end-to-end vector distribution
is one in which every bond vector itself is Gaussianly distributed . The probability distribution in configuration space
then is

One may think of this model as a coarse grained model of a polymer, where like in the previous section, every vector actually is the sum of bond vectors, and where is large enough for to be Gaussian. Usually the model is pictured as a chain of

It is a useful exercise to calculate from Eqs. (3.3) and (3.11).