Exact Black Branes in General Dimensions in Higher-Curvature Scalar-Tensor Gravity

Abstract

We obtain two families of neutral planar black branes in a potential-free dilaton-coupled Lovelock--Horndeski theory. Heterotic compactification relates higher-dimensional curvature to scalar dynamics and motivates the interaction structure. At fixed scalar zero mode, the horizon radius and temperature vary while the complete stationary Wald entropy remains constant and positive. The exponential scalar factor at the horizon exactly compensates the area growth, giving this behavior a direct geometric explanation. An exact coefficient analysis determines the two four-dimensional branches and their continuation to every higher dimension through closed coupling relations. The linear family is conformally flat and leaves the AdS scale free at fixed couplings; the fractional family is Weyl curved and fixes that scale. The common kinetic relation also excludes their realization through a real one-scalar flat-torus reduction of a metric--dilaton parent.