NUMERICAL ANALYSIS OF GRAVITATIONAL WAVES IN HORNDESKI THEORY USING RANDOM PARAMETERIZATION

• Main Author: Baharuddin Rusyda, Muhammad
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/61906
• Institution: Institut Teknologi Bandung

Modified gravity was first proposed to explain the theoretical side of the acceleration of the expansion of the universe. Currently, universal description that combines dark energy and modified gravity in a modification by a scalar field is called the scalar-tensor theory. More specifically, the Horndeski theory is the most general class of these theories. Lombriser and Taylor (Lombriser dan Taylor, 2016), and Bettoni, et al. (Bettoni dkk., 2017) have reported that gravitational waves (GW) detections have the potential to select models of the Horndeski theory that fits observational results. According to these articles, detection of the phase velocity of GW symbolised as, ????????, can exclude a lot of the models. This is because those models predict ???????? value that is significantly different from the speed of light. In this thesis, following the framework given by Arai and Nishizawa (Arai dan Nishizawa, 2018), ???????? parameterization by Bellini and Sawicky (Bellini dan Sawicki, 2014) was used to describe the Horndeski theory and the arbitrary function ???????? of the scalar field coupling terms were taken to be polynomial in ???? and ????=??????????????????. In this case, the coefficients of ???????? were used as the model parameters to then determine the value of the physical parameter ????????. Direct random method was then applied to the model parameters, and then parameters that satisfied the consistency and stability condition were kept. The corresponding observables of the ???????? parameters were then compared to the observational results of GW170817. Simulation has been done for two specific models of the Horndeski theory, that is the non-minimal coupling (NMC) model and the non-minimal derivative coupling (NMDC) model with ~2000 data for each model. Analysis of the NMC model gives ???????? values that deviates significantly from speed of light, while the NMDC model gives result that satisfies the observational constraints of GW.