Testing O(D,D) string cosmology based on double field theory

Abstract: The low-energy limit of string theory contains additional gravitational degrees of freedom, the B-field and dilaton, that are not present in general relativity. Together with the metric, these three fields are naturally embedded in the $\mathbf{O}(D,D)$-symmetric framework of double field theory (DFT). Furthermore, extending the $\mathbf{O}(D,D)$ symmetry to additional matter fixes a modified minimal coupling in string frame and leads to a DFT version of Einstein's equations, in which the resulting DFT energy-momentum tensor is enhanced to include dilaton pressure and skew-symmetric contributions. After reviewing the DFT framework, I will explore its cosmological implications: I will describe how homogeneous and isotropic backgrounds can be characterized by two equation-of-state parameters, and I will present some analytic solutions that provide candidate models for bouncing cosmologies. Then I will discuss recent progress toward testing $\mathbf{O}(D,D)$ cosmology, including implications for structure formation, luminosity distance measurements, and a possible non-Riemannian origin of the universe.

general relativity and quantum cosmologyHEP - theorymathematical physicsdifferential geometry

Audience: advanced learners

( paper )

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Europe and Pacific Theoretical Physics

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