Thermal/quantum effects and induced superstring cosmologies Original Research Article

We consider classical superstring theories on flat four-dimensional space–times, and where image or image supersymmetry is spontaneously broken. We obtain the thermal and quantum corrections at the string one-loop level and show that the back-reaction on the space–time metric induces a cosmological evolution. We concentrate on heterotic string models obtained by compactification on a image torus and on image orbifolds. The temperature T and the supersymmetry breaking scale M are generated via the Scherk–Schwarz mechanism on the Euclidean time cycle and on an internal spatial cycle respectively. The effective field theory corresponds to a no-scale supergravity, where the corresponding no-scale modulus controls the SUSY-breaking scale. The classical flatness of this modulus is lifted by an effective thermal potential, given by the free energy. The gravitational field equations admit solutions where M, T and the inverse scale factor image of the universe remain proportional. In particular the ratio image is fixed during time evolution. The induced cosmology is governed by a Friedmann–Hubble equation involving an effective radiation term image and an effective curvature term image, whose coefficients are functions of the complex structure ratio image.