TY - JOUR
T1 - Dark energy and cosmological solutions in second-order string gravity
AU - Calcagni, Gianluca
AU - Tsujikawa, Shinji
AU - Sami, M.
N1 - Copyright:
Copyright 2005 Elsevier B.V., All rights reserved.
PY - 2005/10/7
Y1 - 2005/10/7
N2 - 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.
AB - 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.
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U2 - 10.1088/0264-9381/22/19/011
DO - 10.1088/0264-9381/22/19/011
M3 - Article
AN - SCOPUS:25444470777
VL - 22
SP - 3977
EP - 4006
JO - Classical and Quantum Gravity
JF - Classical and Quantum Gravity
SN - 0264-9381
IS - 19
ER -