UJI PENDEKATAN KOSMOGRAFI DALAM REKONSTRUKSI DYNAMICAL DARK ENERGY

• Main Author: Farrel Savero, Muhammad
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/66041
• Institution: Institut Teknologi Bandung

Various models of dynamical dark energy (DDE) with energy density evolves with time have been proposed, either with constant w but not equal to 1, or w that changes with time. DDE models with changing w are proposed both based on formal theories and phenomenological considerations, and are generally represented in the form of an exact equation, and then fitted with observation data. A model independent approach to reconstruct the dark energy directly from the observed data is necessary. One way to do this is to conduct a kinematics review of the the evolution of the universe in the cosmographic method. Cosmography originally was based on on the expansion of the Taylor series with respect to the scale factor as a function of time and only assumes that the Friedmann Lemaitre Robertson Walker (FLRW) metric is valid. Using this method, we have obtained for example, the parameter deceleration of the universe from supernova Ia data, which states that the universe is expanding at an accelerating rate. A cosmographic approach is expected to help in providing direction for the development of more formal models for dark energy. However, cosmography using Taylor expansion has a major problem concerning convergence, i.e. applies only to redshift z < 1 and truncation. Various other forms of expansion/polynomials are proposed to overcome Taylor expansion problems in cosmographic approach. This Final Project is focusing on testing the behavior of various expansions/polynomials which can be used in cosmographic methods to solve the main problems in cosmography and to reconstruct various DDE parameterization models, namely wCDM, Chevalier- Linder-Polarski (CPL), and Jassal-Bagla-Padmanabhan (JBP). To achieve this goal, type Ia supernova data, Observational Hubble Data (OHD), and Gamma Ray Burst (GRB) are used. Bayesian Statistics with MCMC algorithm is employed for statistical analysis. Obtained Taylor seriesdepends on the dynamical model of dark energy and also the cosmological probes that wants to approximated, y-redshift series tend not to depend on the model and depends only on the cosmological probes that are proxied, while for the polynomials Pad´e and Chebyshev it was found that these polynomaries were effective used to approach cosmological magnitudes in high redshifts. Did also solve the best constraints obtained using y2-redshift series and the SN Ia + OHD + GRB data is H0 = 74, 160,31 ?0,31, q0 = ?1, 70,06 ?0,06, dan j0 = ?11, 270,91 ?0,91.