We consider the quadratic effective energy-momentum tensor that plays the role of cosmological back-reaction. We evaluate this from the cosmological perturbations during inflation. We present the recent results in uniform-expansion and uniform-density gauge conditions, and compare with the previous results in other (longitudinal, spatially-flat, comoving) gauge conditions.
We study a string-motivated theoretical prior on the quintessential dark energy model with exponential potential, ( V(φ) = V₀ e^-λ φ ), allowing for non-zero spatial curvature. First, we formulate the corresponding dynamical system and investigate its cosmological evolution numerically, illustrating the phase-space behaviour and the influence of curvature on the background dynamics. In open...
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...
