Number of Subtractions in Fixed-Transfer Dispersion Relations

Assuming the minimal requirements necessary to derive the Froissart bound, the number of subtractions for the fixed-momentum-transfer dispersion relation in the unphysical region $0<t<\mathrm{}4\mathrm{}{\mu }^2$ turns out to be 2. In the proof, the positiveness of all the derivatives of absorptive part with respect to $t$ at $t=0\mathrm{}$ is used. Physical implications and applications of this result are briefly discussed.