No small hairs in anisotropic power law Gauss-Bonnet inflation

We will examine whether anisotropic hairs exist in a string-inspired scalar-GaussBonnet gravity model with the absence of potential of scalar field during the inflationary phase. As a result, we are able to obtain the Bianchi type I power-law solution to this model under the assumption that the scalar field acts as the phantom field, whose kinetic is negative definite. However, the obtained anisotropic hair of this model turns out to be large, which is inconsistent with the observational data.