ON THE EMERGENCE OF FRACTAL COSMIC SPACE FROM FRACTIONAL QUANTUM GRAVITY
Emergent cosmology; Schwarzschild black hole; fractional quantum cosmology;
dark matter.
This dissertation investigates a cosmological model that explains the observational
data on the matter content of the Universe using Padmanabhan’s theory of emergent cosmology
and insights from fractional quantum gravity applied to the Schwarzschild black
hole. Two main directions lead to this model. On the one hand, we start with the Hamiltonian
formalism of general relativity and the canonical quantization of the theory leading
to the Wheeler-DeWitt equation. A spherically symmetric spacetime then simplifies the
application of the Wheeler-DeWitt equation and we can investigate the quantization of the
Schwarzschild black hole, its mass spectrum, and thermodynamics, in the semi-classical
limit. The study of fractals and the use of the Riesz fractional derivative via fractional
quantum gravity show that the surface area of the event horizon of the Schwarzschild black
hole has a random fractal structure, whose description is possible by fractional quantities.
On the other hand, we show that the apparent cosmological horizon provides both
a Hawking temperature associated with the horizon of an FLRW spacetime and is the
most suitable horizon for obtaining the Friedmann equations with Padmanabhan’s theory
in which cosmic space and its expansion emerge due to the tendency to satisfy the holographic
principle. Finally, due to the results indicated by fractional quantum cosmology,
we argue the following proposition: the cosmological apparent horizon of the Universe
has the same structure of a random fractal as the event horizon of the Schwarzchild black
hole. This leads to modified Friedmann equations that reveal an effect of fractal geometry
that amplifies the content of baryonic matter already existing in the Universe and thus
simulates the additional content of matter that we currently call dark matter.