We discuss the discrete spectrum of N particles in a curved planar waveguid
e. If they are neutral fermions, the maximum number of particles that the w
aveguide can bind is given by a one-particle Birman-Schwinger bound in comb
ination with the Pauli principle. On the other hand, if they are charged, e
.g., electrons in a bent quantum wire, the Coulomb repulsion plays a crucia
l role. We prove a sufficient condition under which the discrete spectrum o
f such a system is empty. (C) 1999 American Institute of Physics. [S0022-24
88(99)01309-2].