On 17 August 2021 Daniel Kristoffer Blixt will defend his PhD thesis "Hamiltonian analysis of covariant teleparallel theories of gravity" in Physics.
Dr. Manuel Hohmann (UTIP)
Prof. Rafael Ferraro (IAFE CONICET-UBA and Buenos Airese University, Argentina)
Dr. Yuri Obukhov (IBRAE, Russian Academy of Sciences, Moscow, Russia)
For over a century, it has been known that gravity should be described by the theory of general relativity, in which matter is affecting the spacetime geometry we live in, rather than as a force theory. This description has been proven to pass much experimental and observational tests since Albert Einstein formulated this theory of gravity. Furthermore, it has been proven successful as incorporated in the standard model of cosmology. However, recently it has become evident from observation that there are statistically significant tensions in observations within the standard model of cosmology. Furthermore, 95% of our universe consists of dark matter and dark energy, which is still not understood. In order to address these issues one may look into modified theories of gravity. In this thesis teleparallel modified theories of gravity are examined. They make use of the fact that there are alternative physically equivalent descriptions of general relativity. However, the teleparallel formulation admits new ways to modify gravity. In particular a theory called f(TNGR)-gravity is examined. The question this thesis address is if f(TNGR )-gravity is viable as a theory from a theoretical point of view. In order to answer this question the so-called covariant Hamiltonian analysis of the theory is considered for the first time. This theory is more correct and general from a fundamental perspective and it might lead to different conclusions than for those found in the literature. The first part in the Hamiltonian analysis for f(TNGR)-gravity is explicitly derived. This paves the way for a canonical Hamiltonian analysis for the most popular theories of teleparallel gravity. The main conclusion of the thesis is that the viability of f(TNGR)-gravity is in serious doubt. Though, there are still a few points that need to be examined before ruling out f(TNGR) as a viable theory of gravity.