Perfect metal phases of one-dimensional and anisotropic higher-dimensional systems

We show that a one-dimensional quantum wire with 23 channels of interacting fermions has a perfect metal phase in which all weak perturbations that could destabilize this phase are irrelevant. Consequently, weak disorder does not localize it, a weak periodic potential does not open a gap, and contact with a superconductor also fails to open a gap. Similar phases occur for $N\ge 24$ channels of fermions, except for $N=25$, and for $8k$ channels of interacting bosons, with $k\ge 3$. Arrays of perfect metallic wires form higher-dimensional fermionic or bosonic perfect metals, albeit highly anisotropic ones.