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Research output: Contribution to Journal/Magazine › Journal article › peer-review
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TY - JOUR
T1 - Gauss-Bonnet Dark Energy and the speed of gravitational waves
AU - Terente Diaz, Jose
AU - Dimopoulos, Konstantinos
AU - Karciauskas, Mindaugas
AU - Racioppi, Antonio
PY - 2023/10/10
Y1 - 2023/10/10
N2 - Gauss-Bonnet Dark Energy has been a popular model to explain the accelerated expansion of the Universe. Quite generically it also predicts the speed of gravitational waves c_GW to be different from the speed of light. This fact alone led some authors to exclude such models in view of the new tight observational constraints on c_GW. However, the behaviour of c_GW depends on the choice of the Gauss-Bonnet (GB) coupling function. It is possible to construct models where c_GW is always equal to the speed of light. More generally, c_GW is a time dependent function with instances where both speeds coincide. Nevertheless, we observe that the bound on c_GW excludes scenarios where the GB term directly affects the expansion of the Universe, even if the constraint on the variation of the coupling function does not appear to be strong. We perform the dynamical systems analysis to see if the expansion of the Universe could be affected indirectly by modulating the behaviour of the scalar field, which modulates the GB coupling. It is shown that either the bounds on c_GW are violated by many orders of magnitude, or it might be very difficult to find models that are consistent with other cosmological observations.
AB - Gauss-Bonnet Dark Energy has been a popular model to explain the accelerated expansion of the Universe. Quite generically it also predicts the speed of gravitational waves c_GW to be different from the speed of light. This fact alone led some authors to exclude such models in view of the new tight observational constraints on c_GW. However, the behaviour of c_GW depends on the choice of the Gauss-Bonnet (GB) coupling function. It is possible to construct models where c_GW is always equal to the speed of light. More generally, c_GW is a time dependent function with instances where both speeds coincide. Nevertheless, we observe that the bound on c_GW excludes scenarios where the GB term directly affects the expansion of the Universe, even if the constraint on the variation of the coupling function does not appear to be strong. We perform the dynamical systems analysis to see if the expansion of the Universe could be affected indirectly by modulating the behaviour of the scalar field, which modulates the GB coupling. It is shown that either the bounds on c_GW are violated by many orders of magnitude, or it might be very difficult to find models that are consistent with other cosmological observations.
KW - modified gravity
KW - cosmology
KW - gravitational waves
KW - quintessence
KW - Gauss-Bonnet
U2 - 10.1088/1475-7516/2023/10/031
DO - 10.1088/1475-7516/2023/10/031
M3 - Journal article
VL - 10
JO - Journal of Cosmology and Astroparticle Physics
JF - Journal of Cosmology and Astroparticle Physics
SN - 1475-7516
M1 - 031
ER -