TY  - JOUR
A1  - Schmidt, Hans-Jürgen
A1  - Singleton, Douglas
T1  - Isotropic universe with almost scale-invariant fourth-order gravity
T2  - Journal of mathematical physics
N2  - We study a class of isotropic cosmologies in the fourth-order gravity with Lagrangians of the form L = f(R) + k(G) where R and G are the Ricci and Gauss-Bonnet scalars, respectively. A general discussion is given on the conditions under which this gravitational Lagrangian is scale-invariant or almost scale-invariant. We then apply this general background to the specific case L = alpha R-2 + beta Gln G with constants alpha, beta. We find closed form cosmological solutions for this case. One interesting feature of this choice of f(R) and k(G) is that for very small negative value of the parameter beta, the Lagrangian L = R-2/3 + beta Gln G leads to the replacement of the exact de Sitter solution coming from L = R-2 (which is a local attractor) to an exact, power-law inflation solution a(t) = t(p) = t(-3/beta) which is also a local attractor. This shows how one can modify the dynamics from de Sitter to power-law inflation by the addition of a Gln G-term.
Y1  - 2013
UR  - https://publishup.uni-potsdam.de/frontdoor/index/index/docId/34956
SN  - 0022-2488
VL  - 54
IS  - 6
PB  - American Institute of Physics
CY  - Melville
ER  -