R^4 Corrections to Heterotic M-theory
  We study R^4 corrections in heterotic M-theory. We derive to order kappa^{4/3} the induced modification to the Kahler potential of the universal moduli and its implications for the soft supersymmetry breaking terms. The soft scalar field masses still remain small for breaking in the T-modulus direction. We investigate the deformations of the background geometry due to the R^4 term. The warp-factor deformation of the background M_4 x CY(3) x S^1/Z_2 can no longer be integrated to a fully non-linear solution, unlike when neglecting higher derivative corrections. We find explicit solutions to order kappa^{4/3} and, in particular, find the expected shift of the Calabi-Yau volume by a constant proportional to the Euler number. We also study the effect induced by the R^4 terms on the de Sitter vacua found previously by balancing two non-perturbative contributions to the superpotential, namely open membrane instantons and gaugino condensation. To order kappa^{4/3} all induced corrections are proportional to the Euler number of the Calabi-Yau three-fold. 
Lilia Anguelova, Diana Vaman