Imponente, Giovanni
(2003)
Fingerprints of the Very Early Universe.
[Tesi di dottorato]
(Inedito)
[error in script]
[error in script]
Tipologia del documento: 
Tesi di dottorato

Lingua: 
English 
Titolo: 
Fingerprints of the Very Early Universe 
Autori: 
Autore  Email 

Imponente, Giovanni  [non definito] 

Data: 
2003 
Tipo di data: 
Pubblicazione 
Numero di pagine: 
184 
Istituzione: 
Università degli Studi di Napoli Federico II 
Dipartimento: 
Scienze fisiche 
Dottorato: 
Fisica fondamentale ed applicata 
Ciclo di dottorato: 
16 
Coordinatore del Corso di dottorato: 
nome  email 

Sciarrino, Antonio  [non definito] 

Tutor: 
nome  email 

Marmo, Giuseppe  [non definito] 

Data: 
2003 
Numero di pagine: 
184 
Parole chiave: 
cosmologia, universo primordiale, big bang, mixmaster,
soluzione quasiisotropa, inflation, quantum gravity 
Settori scientificodisciplinari del MIUR: 
Area 02  Scienze fisiche > FIS/05  Astronomia e astrofisica 
Depositato il: 
24 Ott 2005 
Ultima modifica: 
01 Dic 2014 12:35 
URI: 
http://www.fedoa.unina.it/id/eprint/139 
DOI: 
10.6092/UNINA/FEDOA/139 
Abstract
During the work developed in the PhD Thesis, it has been faced a number of problems
concerning theoretical cosmology especially with respect dynamical evolution of the Universe
near the cosmological singularity.
Wide space has been devoted to the study of the subtle question concerning the covariance
chaoticity, which led to important issues favourable to the independence of the ‘’chaos’’ with
respect to the choice of the temporal gauge. Such analysis found its basis either on the
standard approach using the Jacobi metric (a scheme allowed by the existence of an energy
like constant of motion), either by a statistical mechanics approach in which the mixmaster
evolution is represented as a billiard on a Lobatchevski plane and therefore admitting a
microcanonical ensemble associated to such energylike constant.
Furthermore, an important step consisted in searching a Physical link between the chaoticity
characterizing the system at a classical level and the quantum indeterminism appearing in the
Planckian era for such a model. More precisely it was constructed che canonical quantization of
the model via a Schroedinger approach (equivalent to the WheelerDeWitt scheme) and then
developed the WKB semiclassical limit to be compared with the classical dynamics. As an
issue, it resulted a correspondence between the continuity equation of the microcanonical
distribution function and that one describing the dynamics of the first order corrections in the
wave function for h 0.
It is remarkable the investigation performed about a quasiisotropic inflationary solution, which
allowed to confirm how there is non chance for classical inhomogeneous perturbations to
survive after the DeSitter phase; such an analysis supports strongly the idea that only quantum
fluctuations ofthe scalar field can provide a satisfactory esplanation for the observed spectrum
of inhomogeneous perturbations.
A detailed discussion was pursued in view of clarifying the peculiarity existing to characterize
chaos in General Relativity; in particular, it has been provived a critical discussion on the
predictivity allowed by the fractal basin boundary approach in qualifying the nature of the
mixmaster dynamics; the main issue on this direction relies on the numerical approximations
limits when treating iterations of irrational numbers and overall on the potential methods
commonly adopted in the dynamical systems approach.
With this respect it is emphasized the ambiguity of describing chaos in terms of geodesic
deviation when the backgroun metric is a pseudo Riemannian one; a correct characterization of
the Lyapunov exponents required a projection of the connecting vector toward a Fermi basis.
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