Dark energy and cosmological solutions in second-order string gravity
Dark energy and cosmological solutions in second-order string gravity
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DOI：
10.1088/0264-9381/22/19/011
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发表时间：
2005-05
影响因子：
3.5
通讯作者：
G. Calcagni;S. Tsujikawa;M. Sami
中科院分区：
文献类型：
--
作者：
G. Calcagni;S. Tsujikawa;M. Sami
We study the cosmological evolution based on a D-dimensional action in low-energy effective string theory in the presence of second-order curvature corrections and a modulus scalar field (a dilaton or compactification modulus). A barotropic perfect fluid coupled to the scalar field is also allowed. Phase space analysis and the stability of asymptotic solutions are performed for a number of models which include (i) a fixed scalar field, (ii) a linear dilaton in the string frame, and (iii) a logarithmic modulus in the Einstein frame. We confront analytical solutions with observational constraints for the deceleration parameter and show that Gauss–Bonnet gravity alone (i.e., with no matter fields) may not explain the current acceleration of the universe. We also study the future evolution of the universe using the Gauss–Bonnet parametrization and find that big rip singularities can be avoided even in the presence of a phantom fluid because of the balance between the fluid and curvature corrections. A non-minimal coupling between the fluid and the modulus field also opens up the interesting possibility of avoiding a big rip regardless of the details of the fluid equation of state.
