GAUGE AND GROUP PROPERTIES OF MASSLESS FIELDS IN ANY DIMENSION

It is shown that the solvable structure of the stability group of a ma ssless field yields, in a simple and short way, useful information abo ut the physical polarization states and the structure of the Hilbert s pace for such a field. It is also shown that such fields are necessari ly gauge fields; the exact form of the gauge transformation follows fr om the structure of the equivalence classes implied by the group prope rties. Some examples for spinor and tensor fields in general dimension s are worked out and the structure of the Hilbert space for gravitatio nal radiation is discussed in some detail.