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<4μ² turns out to be 2. In the proof, the positiveness of all the derivatives of absorptive part with respect to t at $t=0$ is used. Physical implications and applications of this result are briefly discussed.