Can the Interaction between Baby Universes Generate a Big Universe?

We explore a simple toy model of interacting universes to establish that a small baby universe could become large ($\gg$ Planck length) if a third quantization mechanism is taken into account.Comment: 4 pages, PLAIN-TEX, Ref: SISSA 104/94/A, to be published in Int. Jou. Mod. Phys.

Two-dimensional correlation function of binary black hole coalescences

We compute the two-dimensional correlation functions of the binary black hole coalescence detections in LIGO-Virgo's first and second observation runs. The sky distribution of binary black hole coalescence events is tested for correlations at different angular scales by comparing the observed correlation function to two reference functions that are obtained from mock datasets of localization error regions uniformly distributed in the sky. No excess correlation at any angular scale is found. The power-law slope of the correlation function is estimated to be $\gamma= 2.24\pm 0.33$ at the three-$\sigma$ confidence level, a value consistent with the measured distribution of galaxies.Comment: 11 pages, 4 figures, final published versio

How classical are TeV-scale black holes?

We show that the Hawking temperature and the entropy of black holes are subject to corrections from two sources: the generalized uncertainty principle and thermal fluctuations. Both effects increase the temperature and decrease the entropy, resulting in faster decay and ``less classical'' black holes. We discuss the implications of these results for TeV-scale black holes that are expected to be produced at future colliders.Comment: 10 pages, no figures, REVTeX style. Extra comments and references to match version accepted to Classical and Quantum Gravit

Cosmic Black Holes

Production of high-energy gravitational objects is a common feature of gravitational theories. The primordial universe is a natural setting for the creation of black holes and other nonperturbative gravitational entities. Cosmic black holes can be used to probe physical properties of the very early universe which would usually require the knowledge of the theory of quantum gravity. They may be the only tool to explore thermalisation of the early universe. Whereas the creation of cosmic black holes was active in the past, it seems to be negligible at the present epoch.Comment: 7 pages. Essay submitted to the 2003 Gravity Research Foundation essay competition. Received an honorable mention. Accepted for publication in IJMP

Quantization of a 2D Minisuperspace Model in Dilaton-Einstein Gravity

We investigate a minisuperspace model of Einstein gravity plus dilaton that describes a static spherically symmetric configuration or a Kantowski - Sachs like universe. We develop the canonical formalism and identify canonical quantities that generate rigid symmetries of the Hamiltonian. Quantization is performed by the Dirac and the reduced methods. Both approaches lead to the same positive definite Hilbert space.Comment: 10 pages, plain tex, no figure

On a Quantum Universe Filled with Yang - Mills Radiation

We investigate the properties of a quantum Robertson - Walker universe described by the Wheeler -- DeWitt equation. The universe is filled with a quantum Yang -- Mills uniform field. This is then a quantum mini copy of the standard model of our universe. We discuss the interpretation of the Wheeler -- DeWitt wave function using the correspondence principle to connect $\vert\psi\vert^2$ for large quantum numbers to the classical probability for a radiation dominated universe. This can be done in any temporal gauge. The correspondence principle determines the Schr\"odinger representation of the momentum associated to the gravitational degree of freedom. We also discuss the measure in the mini--superspace needed to ensure invariance of the quantum description under change of the temporal gauge. Finally, we examine the behaviour of $\vert\psi\vert^2$ in inflationary conditions.Comment: 12 pages, PLAIN-TEX, Report: DFTT 23/9