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Paper IPM / P / 17198  


Abstract:  
A novel 4dimensional EinsteinâGaussâBonnet (4D EGB) gravity has been proposed that asserts to bypass the Lovelockâs theorem and to result in a nontrivial contribution to the gravitational dynamics in fourdimensional spacetime. Although inconsistencies have been raised for this theory in nonlinear perturbation limits, the results of the consistent 4D EGB model indicate that the background equations and the linear scalar modes are in good agreement with the initial 4D EGB model. In this work, we study the integrated SachsâWolfe (ISW) effect, as a linear phenomenon, in the 4D EGB model. For this purpose, we calculate the evolution of the gravitational potential and the linear growth factor as a function of redshift for the 4D EGB model and compare it with the corresponding result obtained from the cold dark matter (CDM) model. We also calculate the ISWauto power spectrum and the ISWcross power spectrum as functions of cosmic microwave background (CMB) multipoles for the 4D EGB model and compare those with the one obtained from the CDM model. To do this, we use the strongest constraint on the coupling parameter proposed for the 4D EGB model. Additionally, to calculate the ISW effect for the 4D EGB model, we employ three largescale structure surveys from different wavelengths. The results exhibit that the ISW effect in the 4D EGB model is higher than the one obtained from the CDM model. Hence, we show that the 4D EGB model can amplify the amplitude of the ISW power spectrum, which can be considered as a relative advantage of the 4D EGB model comparing the CDM one. Also, we indicate that the deviation from the CDM model is directly proportional to the value of the dimensionless coupling parameter .
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