  In 1975, Carleial presented a special case of an interference channel in
which the interference does not reduce the capacity of the constituent
point-to-point Gaussian channels. In this work, we show that if the
inequalities in the conditions that Carleial stated are strict, the dispersions
are similarly unaffected. More precisely, in this work, we characterize the
second-order coding rates of the Gaussian interference channel in the strictly
very strong interference regime. In other words, we characterize the speed of
convergence of rates of optimal block codes towards a boundary point of the
(rectangular) capacity region. These second-order rates are expressed in terms
of the average probability of error and variances of some modified information
densities which coincide with the dispersion of the (single-user) Gaussian
channel. We thus conclude that the dispersions are unaffected by interference
in this channel model.
