CONFORMAL THEORY OF M2, D3, M5 AND D1+D5 BRANES

The bosonic actions for M2, D3 and M5 branes in their own d-dimensiona l near-horizon background are given in a manifestly SO(p+1,2) x SO(d-p -1) invariant form (p = 2,3,5). These symmetries result from a breakdo wn of ISO(d, 2) (with d = 10 for D3 and d = 11 for M2 and M5) symmetry by the Wess-Zumino term and constraints. The new brane actions, reduc e after gauge-fixing and solving constraints to (p+1) dimensional inte racting field theories with a non-linearly realized SO(p+1;2) conforma l invariance. We also present an interacting two-dimensional conformal field theory on a D-string in the near-horizon geometry of a D1+D5 co nfiguration.