Gauge Fixing and Scattering Amplitudes in String Field Theory Expanded around Universal Solutions

We study a gauge fixed action of open string field theory expanded around the universal solution which has been found as an analytic classical solution with one parameter a. For a>-1/2, we are able to reproduce open string scattering amplitudes in the theory fixed in the Siegel gauge. At a=-1/2, all scattering amplitudes vanish and there is no open string excitation in the gauge fixed theory. These results support the conjecture that the universal solution can be regarded as pure gauge or the tachyon vacuum solution.