Speaker
Description
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 O(D,D)-symmetric framework of double field theory (DFT). Furthermore, extending the 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 formalism, 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 O(D,D) cosmology, including implications for structure formation, luminosity distance measurements, and a possible non-Riemannian origin of the universe.
