Linear and non-linear effects in structure formation

  • Irene Milillo

Student thesis: Doctoral Thesis


The subject matter of this thesis is the formation of large-scale structure in the universe. Most of the study has dealt with the non-linear evolution of cosmological uctuations, focusing on the scalar sector of perturbation theory.
The period of transition between the radiation era and the matter era has been largely examined, extending the already known linear results to a nonstandard matter model and to a non-linear analysis. The obtained second order solutions for the matter uctuations variables have been used to find the skewness of the density and velocity distributions, an important statistical estimator measuring the level of non-Gaussianity of a distribution.
In the context of cosmological perturbations, a complete Post-Newtonian (1PN) treatment is presented with the aim of obtaining a set of equations suitable in particular for the intermediate scales. The final result agrees with both the non linear Newtonian theory of small scales and the linear general relativistic theory of large scales. Analysing the limiting cases of our approach to 1PN cosmology, we have clarified the link between the Newtonian theory of gravity and General Relativity.
This work is the result of the agreement signed by the Department of Physics, University of Roma Tor Vergata and the Institute of Cosmology and Gravitation, University of Portsmouth, United Kingdom in the formal context of the co-tutela project.
The chapters 5, 6 and 7 are the themes of two articles in preparation, that will be shortly submitted:
� How the universe got its skewness" - M. Bruni, I.Milillo, K.Koyama
� Post-Newtonian Cosmology" - I. Milillo, D.Bertacca, M. Bruni
Date of AwardSept 2010
Original languageEnglish
Awarding Institution
  • University of Portsmouth
SupervisorMarco Bruni (Supervisor), David Wands (Supervisor) & Roy Maartens (Supervisor)

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