In this review, we focus on whether a canonical quantization of general relativity can
produce testable predictions for cosmology. In particular, we examine how this approach …

A bstract We study bubble of nothing decays and their reverse processes, the creation of
vacua through 'bubbles of something', in models of the Universe based on string theory …

Realizing the no-boundary proposal of Hartle and Hawking as a consistent gravitational
path integral has been a long-standing puzzle. In particular, it was demonstrated by …

A bstract In this paper, we delve into the gravitational path integral of Gauss-Bonnet gravity
in four spacetime dimensions, in the mini-superspace approximation. Our primary focus lies …

We analyze the impact of various boundary conditions on the (minisuperspace) Lorentzian
gravitational path integral. In particular, we assess the implications for the Hartle-Hawking …

We revisit the path-integral approach to the wave function of the Universe by utilizing
Lefschetz thimble analyses and resurgence theory. The traditional Euclidean path integral of …

Recent analysis of quantum cosmology has focused on the Lorentzian path integral
formulations of both the no-boundary and tunneling proposals. However, it has been …

In minisuperspace quantum cosmology, the Lorentzian path integral formulations of the no-
boundary and tunneling proposals have recently been analyzed. But it has been pointed out …

We evaluate the Lorentzian gravitational path integral in the presence of nonvanishing
torsion with the application of the Picard-Lefschetz theory for minisuperspaces …

We study the Hartle-Hawking no-boundary proposal in the framework of Hořava-Lifshitz
gravity. The former is a prominent hypothesis that describes the quantum creation of the …