Partially coherent solitons of variable shape

We present analytical and numerical results related to partially coherent solitons (PCS) of a novel class. In effect, there is freedom to choose the shape of a PCS as it is governed by 2N - 1 parameters, where N is the number of linear modes contributing to the soliton. In particular, we show that a PCS may have an asymmetric shape. The PCS shape becomes arbitrary in the limit of complete incoherence. Another remarkable new feature of a PCS is that collisions in Kerr-like media cause the PCS to change its shape, although each beam remains a stationary soliton after the collision. [S0031-9007(98)07677-7].