Doctoral defence: Laxmipriya Pati „The effects of non-Riemannian connection in teleparallel gravity“

On 26 March at 16:15, Laxmipriya Pati will defend her doctoral thesis "The effects of non-Riemannian connection in teleparallel gravity"

Supervisors:

Dr. Laur Järv, University of Tartu
Dr. Maria Jose Guzman Monsalve, University of Tartu

Opponent:
Dr Syksy Räsanen, University of Tartu (Finland)

Summary
Einstein's theory of general relativity represents a monumental leap in our understanding of gravity, providing a comprehensive framework to explain how mass warps the fabric of spacetime. This theory has successfully accounted for a variety of astronomical phenomena, including the motions in the Solar System, the formation and behavior of black holes, and the bending of light around massive celestial bodies. However, recent observations suggest a dark sector of the Universe, which encompasses both dark matter and dark energy and would make up approximately 95% of its total energy content, yet its nature is still largely unknown. Moreover, the discrepancy in the measurements of the universe's expansion rate (the “Hubble tension”) raises further questions. These unsolved puzzles have motivated researchers to explore modified theories of gravity that may offer alternative explanations.
One intriguing option to venture beyond general relativity is to modify its underlying mathematical premises based on Riemannian geometry, whereby gravity is attributed to spacetime curvature. A key aspect of Riemannian spacetimes is that the connection (the object defining straight lines) is intrinsically linked to the metric tensor (the object defining distances). The PhD thesis focuses on teleparallel theories of gravity, which offer a distinct geometric structure in which gravity is understood as a manifestation of torsion or nonmetricity, rather than curvature. In teleparallel gravity, the connection differs from the Riemannian one, leading to arbitrary degrees of freedom that could be exploited to solve the observed cosmological problems. The thesis investigates the effect of these degrees of freedom in cosmology, and shows that the theory can predict a stable universe that accurately describes nature. Moreover, the freedom in the connection can be used in our favor to simplify the mathematical formulation of the differential equations dictating the nonlinear behavior of spacetime.