A physical interpretation of the Jacobi imaginary transformation and the critical dimension in dual models

It is shown that the Jacobi imaginary transformation occurring in dual loop calculations may be interpreted as a self-consistency condition obtained by assuming a complicated planar Feynman diagram formulation for strings. The self-consistency condition is derived from the intuitive condition that a 'fishnet-diagram' does not change if a free side of the diagram is replaced by the wave function for a string with vacuum quantum numbers. When applying the self-consistency condition to strings for which the spectrum is built up by harmonic oscillators it is seen that the condition is only fulfilled when the number of coupling dimensions is 24. alpha /sub 0/ where alpha /sub 0/ is the intercept. (8 refs).