Gauge Transformation of Double Field Theory for Open String

Understand

We combine symmetry structures of ordinary (parallel directions) and dual (transversal directions) coordinates to construct the Dirac-Born-Infeld (DBI) theory.

• The ordinary coordinates are associated with the Neumann boundary conditions and the dual coordinates are associated with the Dirichlet boundary conditions.
• Gauge fields become scalar fields by exchanging the ordinary and dual coordinates.
• A gauge transformation of a generalized metric is governed by the generalized Lie derivative.