https://doi.org/10.1140/epjc/s10052-025-14813-7
Review
Gravitational core of double field theory
Lecture notes
Department of Physics, Sogang University, 35 Baekbeom-ro, Mapo-gu, 04107, Seoul, Korea
Received:
31
May
2025
Accepted:
16
September
2025
Published online:
7
October
2025
Double Field Theory (DFT) has emerged as a comprehensive framework for gravity, presenting a testable and robust alternative to General Relativity (GR), rooted in the 
symmetry principle of string theory. These lecture notes aim to provide an accessible introduction to DFT, structured in a manner similar to traditional GR courses. Key topics include doubled-yet-gauged coordinates, Riemannian versus non-Riemannian parametrisations of fundamental fields, covariant derivatives, curvatures, and the -symmetric augmentation of the Einstein field equation, identified as the unified field equation for the closed string massless sector. By offering a novel perspective, DFT addresses unresolved questions in GR and enables the exploration of diverse physical phenomena, paving the way for significant future research.
© The Author(s) 2025
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