The structure of galaxies we see in the sky today was seeded in the very early universe. The evolution from initial tiny density perturbations to the cosmic web of voids, clusters and filaments of galaxies tells us about what the universe is made of. There are many ways to utilise this large scale structure to probe cosmology, but measuring the growth rate itself in the nearby universe is...
We compute a holographic entanglement entropy via Ryu-Takayanagi prescription in the three-dimensional Friedmann-Lemaître-Robertson-Walker universe. We consider two types of holographic scenarios analogous to the static patch holography and the half de Sitter holography, in which the holographic boundary is timelike and placed in the bulk. We find in general that the strong subadditivity can...
Primordial gravitational waves (GWs), beyond their direct detection prospects, can induce second-order scalar perturbations. These tensor-induced scalar modes evolve similarly to standard matter perturbations and leave distinct imprints on the large-scale structure (LSS). In this talk, I will present a detailed study of these effects, including analytical results for the evolution of induced...
We study stimulated emission and absorption of gravitons in a squeezed vacuum
state immersed in a thermal radiation bath. Employing one-loop
interaction-picture perturbation theory, we track the time evolution of the
graviton number operator and its expectation value in the squeezed vacuum,
which characterizes the inflationary graviton state. In a Minkowski background
with a thermal bath...
We present a minimal setup within the framework of Horndeski gravity that describes a nonpathological Genesis scenario. Our setup allows for a fully stable transition to the kination epoch, during which General Relativity (GR) is restored. This Genesis scenario circumvents the no-go theorem, albeit at the cost of encountering the risk of strong coupling in the past. Interestingly, our scenario...
