Holographic conformal anomaly and a-theorem in 5D scalar-tensor theories from heterotic strings

Using the coefficient-frame freedom of the O ( α ′ ) heterotic metric-dilaton effective action and incorporating it into Kaluza-Klein reduction with different reduction and maximally symmetric internal spaces, we derive two distinct reduced five-dimensional scalar-tensor branches: a Lovelock-Horndeski-type theory and, for a special coefficient choice, an Einstein-dilaton-Gauss-Bonnet theory. We present a novel derivation of the full holographic conformal anomaly for these two reduced five-dimensional scalar-tensor theories. In the Lovelock-Horndeski case, we also construct exact asymptotically anti–de Sitter (AdS) solutions with linear-dilaton profiles and establish a holographic a-theorem. Our findings show that AdS/CFT remains sound in the presence of nonminimal scalars and higher-curvature terms, with string corrections fixing the conformal anomaly and the dual RG flow.