Novel Extrapolation for Strong Coupling Expansions

We present a novel extrapolation scheme for high order series expansions. The idea is to express the series, obtained in orders of an external variable, in terms of an internal parameter of the system. Here we apply this method to the 1-triplet dispersion in an antiferromagnetic $S=1/2$ Heisenberg ladder. By the use of the internal parameter the accuracy of the truncated series is enhanced tremendously.