Confusion on convention for infinite cylinder geometry

[jflorey]

In the documentations for the triangular lattice (this is also true for other lattices), it is stated under the cylinder_axis property:

For an infinite cylinder

Code: Select all

(bc_MPS=’infinite’ and ``boundary_conditions[1] == ‘open’`)

, this property gives the direction of the cylinder axis, in the same coordinates as the basis, as a normalized vector.

From this, it would sound like the boundary conditions of an infinite cylinder would be ['periodic', 'open']. However, the bc_MPS='infinite' command allegedly takes the infinite direction to be in the x-direction; indeed, the cylinder_axis property returns a unit vector in the x-direction. In that case, an infinite cylinder would seemingly be periodic in the y-direction and open in the x-direction, i.e., ['open', 'periodic'], but this option isn't compatible with bc_MPS='infinite'. On top of all of this, I've found examples in the docs (i.e. the toric code) that claim to work on an infinite cylinder whose boundary conditions are periodic in both directions. Which is it?