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Discontinuity

Discontinuity[s]
is a setting for Part to LoopRefine to compute the discontinuity across the normal threshold cut in channel .

Discontinuity[s,t]
computes the Mandelstam double spectral function in overlapping channels and .

Details and OptionsDetails and Options

  • Gives discontinuities across branch cuts of PVA, PVB, PVC, and PVD. Poles are ignored.
  • The output is always proprtional to the HeavisideTheta function which has support only when the channel is open.
  • Channels of Passarino-Veltman functions are identified by matching patterns s and t to entire arguments of PVA, PVB, PVC, and PVD.
  • A correct result is guaranteed only if all other channels are closed (below normal threshold).
  • Internally, a channel marker is placed in the appropriate arguments of PVA, PVB, PVC, and PVD, and a much simplified form of the Passarino-Veltman reduction formula is applied to obtain the result.