Thick branes in higher-dimensional $f(R)$ gravity

Abstract

We study the thick brane model within $f(R)\sim R^n$ modified gravity in $D$-dimensional spacetimes with $D\geq 6$. The system under consideration consists of two branes orthogonal to each other: the four-dimensional Lorentzian brane and $(D-5)$-dimensional Euclidean one. It is numerically shown that, for a given $D$, regular vacuum asymptotically anti-de Sitter solutions exist only in the range $1<n<D/2$. Depending on the values of $n$ and boundary conditions imposed on the Lorentzian brane, the solutions can pass or not pass through a fixed point located on the Lorentzian brane, and also be $Z_2$-symmetric or nonsymmetric. In the large-$D$ limit, we find approximate analytic solutions. It is also shown that a test scalar field is trapped on the Lorentzian brane at any $D$.