مشخصات پژوهش

We present noncritical Bianchi type I string cosmology solutions in the presence of central charge deficit term Λ. The leading-order string frame curvature appears to be in the high curvature limit Rα0 ≳ 1, which underlines the necessity of including higher-order α0 corrections. We give new solutions of two-loop (firstorder α0) β-function equations of the σ model with nonzero Λ and the dilaton field in both cases of the absence and presence of a spatially homogeneous H field (H ¼ dB). Also, the evolution of solutions is studied in the Einstein frame, in which the string effective action can transform to Gauss-Bonnet gravity model coupled to a dilaton field with potential. We study explicit examples in first-order α0 with chosen values of appeared constants in the solutions and discuss the cosmological implications.