For the symmetric simple exclusion process on an infinite line, we calculate
exactly the fluctuations of the integrated current Qt during time t
through the origin when, in the initial condition, the sites are occupied with
density ρa on the negative axis and with density ρb on the positive
axis. All the cumulants of Qt grow like t. In the range where Qt∼t, the decay exp[−Qt3/t] of the distribution of Qt is
non-Gaussian. Our results are obtained using the Bethe ansatz and several
identities recently derived by Tracy and Widom for exclusion processes on the
infinite line.Comment: 2 figure