Extending a recent result of S.B. Giddings, F. Hacquebord and H. Verlinde, we
show that in the U(N) SYM Matrix theory there exist classical BPS instantons
which interpolate between different closed string configurations via
joining/splitting interactions similar to those of string field theory. We
construct them starting from branched coverings of Riemann surfaces. For the
class of them which we analyze in detail the construction can be made explicit
in terms U(N) affine Toda field theories.Comment: 12 pages, 1 eps figure, JHEP.cls LaTeX2e class file; sign corrected,
ref. and acknowledgements update
