We review, in a historical perspective, some results about black hole spacetimes with a regular center. We then see how their properties are realized in a specific solution that recently appeared; in...
Ansoldi, Stefano, Guendelman, Eduardo I., Shilon, Idan
We present a review of selected topics concerning the creation and evolution of child universes, together with a concise account of some recent progress in the field.
Shell-mediated tunnelling between (anti-)de Sitter vacua (2007)
Ansoldi, Stefano, Sindoni, Lorenzo
We give an extensive study of the tunnelling between arbitrary (anti-)de Sitter spacetimes separated by an infinitesimally thin relativistic shell in arbitrary spacetime dimensions. In particular, we...
Vacuum and semiclassical gravity: a difficulty and its bewildering significance (2007)
We review a long-standing difficulty in some semiclassical models of vacuum and vacuum decay. Surprisingly enough these models, careless of their transparent formulation, are affected by, both,...
Universes out of almost empty space (2007)
Ansoldi, Stefano, Guendelman, Eduardo I.
Baby universes (inflationary or non--inflationary) are regions of spacetime that disconnect from the original ambient spacetime, which we take to be asymptotically flat spacetime. A particular kind...
Shell-mediated tunnelling between (anti-)de Sitter vacua (2007)
Ansoldi, Stefano, Sindoni, Lorenzo
We give an extensive study of the tunnelling between arbitrary (anti-)de Sitter spacetimes separated by an infinitesimally thin relativistic shell in arbitrary spacetime dimensions. In particular, we...
Bubbles and Quantum Tunnelling in Inflationary Cosmology (2007)
We review a procedure to use semiclassical methods in the quantization of General Relativistic shells and apply these techniques in some simplified models of inflationary cosmology. Some interesting...
Braneworlds and Quantum States of Relativistic Shells (2007)
We review some applications of relativistic shells that are relevant in the context of quantum gravity/quantum cosmology. Using a recently developed approach, the stationary states of this general...
Noncommutative geometry inspired charged black holes (2006)
Ansoldi, Stefano, Nicolini, Piero, Smailagic, Anais, Spallucci, Euro
We find a new, non-commutative geometry inspired, solution of the coupled Einstein-Maxwell field equations describing a variety of charged, self-gravitating objects, including extremal and...
Child Universes in the Laboratory (2006)
Ansoldi, Stefano, Guendelman, Eduardo I.
Although cosmology is usually considered an observational science, where there is little or no space for experimentation, other approaches can (and have been) also considered. In particular, we can...
Solitons as Key Parts to Produce a Universe in the Laboratory (2006)
Ansoldi, Stefano, Guendelman, Eduardo I.
Cosmology is usually understood as an observational science, where experimentation plays no role. It is interesting, nevertheless, to change this perspective addressing the following question: what...
The role of a dynamical measure and dynamical tension in brane creation and growth (2005)
Ansoldi, Stefano, Guendelman, Eduardo I., Spallucci, Euro
The use of a non-Riemannian measure of integration in the action of strings and branes allows the possibility of dynamical tension. In particular, lower dimensional objects living in the string/brane...
Gravitational Tunnelling of Relativistic Shells (2004)
Ansoldi, Stefano, Sindoni, Lorenzo
Thin shells in general relativity have been used in the past as keystones to obtain realistic models of cosmological and astrophysical situations. A crucial role for these developments was played by...
Vacuum decay by p-branes production (2004)
Sindoni, Lorenzo, Ansoldi, Stefano
We present a generalization to the N-dimensional case for the nucleation coefficient of a spherical p-brane, separating two (anti-)de Sitter spacetimes. We use a semiclassical approximation based on...
Minisuperspace, WKB, Quantum States of General Relativistic Extended Objects (2004)
The dynamics of relativistic thin shells is a recurrent topic in the literature about the classical theory of gravitating systems and the still ongoing attempts to obtain a coherent description of...
Subject of this thesis is the study of a closed bosonic string: the treatment will follow an approach alternative with respect to the traditional one and stems from a research line pursued in by...
WKB metastable quantum states of a de Sitter--Reissner-Nordstroem dust shell (2003)
We study the dynamics of a spherically symmetric dust shell separating two spacetime domains, the 'interior' one being a part of the de Sitter spacetime and the exterior one having the 'extremal'...
Real and Imaginary Mass Generation in the Presence of External Fields and Axions (2002)
Ansoldi, Stefano, Guendelman, Eduardo I., Spallucci, Euro
Small fluctuations around a constant electric or constant magnetic field F are analyzed in a theory with pseudo scalar [phi] with a coupling g[phi]F~F. It is found that a magnetic external field...
Fuzzy dimensions and Planck's Uncertainty Principle for p-branes (2002)
Aurilia, Antonio, Ansoldi, Stefano, Spallucci, Euro
The explicit form of the quantum propagator of a bosonic p-brane, previously obtained by the authors in the quenched-minisuperspace approximation, suggests the possibility of a novel, unified,...
Ansoldi, Stefano, Milotti, Edoardo
Quantum gravity is quite elusive at the experimental level; thus a lot of interest has been raised by recent searches for quantum gravity effects in the propagation of light from distant sources,...