Clarify background independence and the relation to string field theory

Clarify the precise sense in which the unexpanded doubled-coordinate formulation is background independent and determine how it relates to string-field-theoretic approaches to target-space duality.

Background

The interpolating formulation is written in a background-independent-looking doubled-coordinate form, while moduli dependence emerges after generalized Kaluza–Klein mode expansion. The paper also compares the construction with gauged double field theory and notes its resemblance to string field theory through its tower of generalized Kaluza–Klein modes.

Despite these structural connections, the precise conceptual status of background independence and the relationship to string-field-theoretic descriptions of target-space duality are not settled. The authors explicitly identify both issues as open questions.