Corrigendum: Numerical solutions for the f(R)-Klein–Gordon system (2023 Class. Quantum Grav.40 175009)

Here, the authors correct five typographical errors and one computational error. We shall start by making the necessary typographical corrections and conclude by correcting the computational error.

• Firstly, equation (30) of the main text does not correctly give the Lie derivative of the extrinsic curvature tensor with respect to the normal vector field n . Equation (30) should instead read
  $$\begin{align} \mathcal{L}_{\boldsymbol{n}}K_{ij}& = \!^3R_{ij} - 2K_{il}K^l{}_j + KK_{ij}-\frac1{f_R} \Bigg\{8\pi S_{ij} + \frac12 f\gamma_{ij} + D_iD_j f_R \nonumber \\ & \quad -\frac13\gamma_{ij}[8\pi(S -\rho) + 2f -f_RR]\Bigg\} -\frac{1}{\alpha}D_iD_j\alpha\,. \end{align} \tag{ 1 }$$
• Secondly, in the evolution equation (34) for the extrinsic curvature tensor, the term $\beta^k D_kK_{ij}$ appears twice when it should only appear once.
• Thirdly, equation (66) contains the following typographical error. The fourth term contained in the first set of brackets should be absent.
• Fourthly, equation (69) contains a typographical error and should instead read
  $$\begin{align} \mathcal{H} & =\, \chi^2\Bigg[\bar\Delta^r\phantom{}^{^{\prime}}+\frac{4}{r^2b}+\frac{2b^{^{\prime}}}{b^2r}-\frac{a^{^{\prime\prime}}}{2a^2}+\frac{a^{^{\prime} 2}}{a^3}-\frac{4}{r^2a}+\frac{4\chi^{^{\prime\prime}}}{\chi a}-\frac{6\chi^{^{\prime} 2}}{a\chi^2} \nonumber\\ & \quad -\frac{6b^{^{\prime}}}{rab}-\frac{b^{^{\prime\prime}}}{ab}+\frac{4\chi^{^{\prime}}b^{^{\prime}}}{\chi ab}+\frac{8\chi^{^{\prime}}}{\chi ar} -\frac{2\chi^{^{\prime}}a^{^{\prime}}}{\chi a^2}-\frac{b^{^{\prime} 2}}{2ab^2}\Bigg]+\frac23K^2-\frac32A_a^2\nonumber\\ & \quad -R-\frac{1}{f_R}\Bigg[16\pi\rho-f+\frac{2\chi^2}{a}\Bigg(f_R^{^{\prime\prime}}-f_R^{^{\prime}}\Bigg(\frac{a^{^{\prime}}}{2a}+\frac{\chi^{^{\prime}}}{\chi}-\frac{2}{r}-\frac{b^{^{\prime}}}{b}\Bigg)\Bigg)\Bigg]\,. \end{align} \tag{ 2 }$$
• Lastly, the minus sign in front of the third term in equation (70) should instead be a positive sign.

Regarding the computational error, we have noticed that the evolution equation (84) contains the following error. The factor in front of the $\chi^{^{\prime}}/\chi$ term contained in brackets should have a positive sign. Since our scalar field numerical evolutions were performed with such an error, it is necessary for figures 5–7 to be corrected.

Figures 1, 2 and 3 of this corrigendum should replace, respectively, figures 5, 6 and 7 of the main text. The captions of these figures as well as the Conclusions of the main text do not require any modifications and are still valid for the updated figures.

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