# kwant.wraparound.wraparound¶

kwant.wraparound.wraparound(builder, keep=None, *, coordinate_names='xyz')[source]

Replace translational symmetries by momentum parameters.

A new Builder instance is returned. By default, each symmetry is replaced by one scalar momentum parameter that is appended to the already existing arguments of the system. Optionally, one symmetry may be kept by using the keep argument. The momentum parameters will have names like ‘k_n’ where the ‘n’ are specified by ‘coordinate_names’.

Parameters: builder : Builder keep : int, optional Which (if any) translational symmetry to keep. coordinate_names : sequence of strings, default: ‘xyz’ The names of the coordinates along the symmetry directions of ‘builder’.

Notes

Wraparound is stop-gap functionality until Kwant 2.x which will include support for higher-dimension translational symmetry in the low-level system format. It will be deprecated in the 2.0 release of Kwant.

#### Previous topic

4.5. kwant.wraparound – Wrapping around translational symmetries

#### Next topic

kwant.wraparound.plot_2d_bands