Generalized Ellis-Bronnikov wormhole solution in the scalar-Einstein-Gauss-Bonnet $4d$ gravitational model

Abstract

We consider the sEGB $4d$ gravitational model with a scalar field $\varphi\left(u\right)$, Einstein and Gauss-Bonnet terms. The model action contains a potential term $U\left(\varphi\right)$, a Gauss-Bonnet coupling function $f\left(\varphi\right)$ and a parameter $\varepsilon = \pm 1$, where $\varepsilon = 1$ corresponds to the usual scalar field, and $\varepsilon = -1$ to the phantom field. In this paper, the sEGB reconstruction procedure considered in our previous paper is applied to the metric of the Ellis-Bronnikov solution, which describes a massive wormhole in the model with a phantom field (and zero potential). For this metric, written in the Buchdal parameterization with a radial variable $u$, we find a solution of the master equation for $ f\left(\varphi\left(u\right)\right)$ with the integration (reconstruction) parameter $C_0$. We also find expressions for $U\left(\varphi\left(u\right)\right)$ and $\varepsilon \dot{\varphi}^2 = h\left(u\right)$ for $\varepsilon = \pm 1$. We prove that for all non-trivial values of the parameter $C_0 \neq 0$ the function $h\left(u\right)$ is not of constant sign for all admissible $u \in \left(-\infty , +\infty\right)$. This means that for a fixed value of the parameter $\varepsilon = \pm 1$ there is no non-trivial sEGB reconstruction in which the scalar field is a purely ordinary field ($\varepsilon = 1$) or a purely phantom field ($\varepsilon = - 1$).