NEUMAN-DIRICHLET TADPOLES AS NEW STRING STATES AND QUANTUM-MECHANICALPARTICLE-WAVE DUALITY FROM WORLD-SHEET T-DUALITY

We consider new objects in bosonic open string theory - ND tadpoles, w hich have N(euman) boundary conditions at one end of the world-sheet a nd D(irichlet) at the other, must exist due to s - t duality in a stri ng theory with both NN strings and D-branes. We demonstrate how to int erpolate between N and D boundary conditions. In the case of mixed bou ndary conditions the action for a quantum particle is induced on the b oundary. Quantum-mechanical particle-wave duality, a dual description of a quantum particle in either the coordinate or the momentum represe ntation, is induced by world-sheet T-duality. The famous (R) over tild e = alpha/R relation is equivalent to the quantization of the phase sp ace area of a Planck cell closed integral pdx = 2 pi (h) over bar. We also introduce a boundary operator Z - a ''Zipper'' which changes the boundary condition from N into D and vice versa. (C) 1997 Elsevier Sci ence B.V.