Studies On Interacting Dark Energy Models With A Sign-changeable Coupling

In 1916,the Albert Einstein’s general theory of relativity opened the beginning of the new modern cosmology.Soon after,the expansion of our universe was found sequentially,which directly prompted the establishment of the“Big Bang”theory.With people studying unceasingly on the universe,the result of the observations on supernova type Ia made a big step forward on understanding our universe more clear in 1998.The research indicates that our universe is undergoing an accelerated expansion.On the basis of these the observational facts,a large number of astronomical observations show that there exists a kind of exotic energy component which can not be observed directly,called "dark energy".Dark energy and dark matter totally account for about 95%of the energy of the universe.Due to dark energy and dark matter are detected indirectly by their respective gravitational effects,so we cannot ignore such a significant possibility that there is some direct,non-gravitational interaction between them.The large numbers of research indicated such a possible interaction between dark energy and dark matter had a breakthrough in helping solve(or,at least alleviate)several important theoretical problems of dark energy.In this paper,our study will centre on the interacting dark energy models,and further explore the sign-changeable interacting dark energy scenario by using the latest observational data.Specifically,we consider I∧CDM model and IwCDM model and choose six specific interaction terms,in which the coupling can change sigh during the cosmological evolution.Then,with the help of the latest observation data,we constrain the parameters of those models.The six specific models are explored with(i)Q=b(a)H0ρ0,(ii)Q=b(a)H0ρde,(iii)Q=b(a)H0ρc,(iv)Q=b(a)Hρ0,(v)Q=b(a)Hρde,and(vi)Q=b(a)Hρc.In order to obtain more accurate parameters constrained results and check definite evidence of sign-changeable interaction,the current joint geometric measurement data we use in this work include the JLA compilation of type la supernovae data,the Planck 2015 distance priors data of cosmic microwave background observation,the baryon acoustic oscillations measurements,and the direct measurement of the Hubble constant.In addition,in order to avoid this influence cased by the number of parameters,we employ the Akaike information criterion and Bayesian information criterion in the process of model comparison and analysis.We find that,for all the models,we have b0<0 and be>0 at around the 1σ level,and so b0 and be are in extremely strong anti-correlation.So we reconstruct the evolution of the coupling b(z)with 1σ uncertainties.Our results show that the coupling changes sign during the evolution at about the 1σ level and the sign of b(z)transits from positive value to negative value.That is,the energy transfer is from dark matter to dark energy when dark matter dominates the universe and the energy transfer is from dark energy to dark matter when dark energy dominates the universe.The conclusions are consistent with the results from IwCDM models basically.In addition,Q(a)=b(a)H0ρc is the best fitted with the current observations.Finally,through the analysis of the equation-of-state parameters ω0 and ω(a)in IACDM model and ICPL model,we find out the latest observations tend to a vacuum energy,which change over time.