Brane tensions and coupling constants from within M-theory

Reviewing the cancellation of local anomalies of M-theory on R-10 x S-1/Z(2), the Yang-Mills coupling constant on the boundaries is rederived. The result is lambda(2) = 2(1/3)(2 pi)(4 pi kappa(2))(2/3) corresponding to eta = lambda(6)/kappa(4) = 256 pi(5) in the "upstairs" units used by Horava and Witten and differs from their calculation. It is shown that these values are compatible with the standard membrane and fivebrane tensions derived from the M-theory bulk action. In view of these results it is argued that the natural units for M-theory on R-10 x S-1/Z(2) are the "downstairs" units where the brane tensions take their standard form and the Yang-Mills coupling constant is lambda(2) = 4 pi(4 pi kappa(2))(2/3). (C) 1998 Elsevier Science B.V.