  Following recent work of Halperin, Lee, and Read, and Kalmeyer and Zhang, a
double-layer electron system with total Landau-level filling factor $\nu=1/2$
is mapped onto an equivalent system of fermions in zero average magnetic field
interacting via a Chern-Simons gauge field. Within the random-phase
approximation a new, low-lying, diffusive mode, not present in the $\nu=1/2$
single-layer system, is found. This mode leads to more singular low-energy
scattering than appears in the single layer system, and to an attractive
pairing interaction between fermions in different layers which grows stronger
as the layer spacing is decreased. The possible connection between this pairing
interaction and the experimentally observed fractional quantum Hall effect in
double-layer systems is discussed.
