Cosmological effects induced by quantized fields

Author(s)

Yul Otani

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Física (IF/SBI)
• Defense date: 2010-09-30

Examining board members

Joao Carlos Alves Barata; Elcio Abdalla; Daniel Augusto Turolla Vanzella

• Advisor: Joao Carlos Alves Barata

Abstract

The present dissertation reviews the coupling of a scalar non-interacting quantum field with the metric of a FLRW(Friedmann-Lemaítre-Robertson-Walker) spacetime, proposed in a work by C. Dappiaggi, K. Fredenhagen and N. Pinamonti. We present methods for the quantization of a real Klein-Gordon field in globally hyperbolic spacetimes and discuss procedures for the point-splitting regularization of the stress-energy tensor. We consider those fields in FLRWspacetimes and point out adiabatic states with mean field fluctuation given by h2i = m2+R, with ; being constants that emerge from the regularization procedure. The backreaction of the quantum field provides a diferential equation for the Hubble parameter given by _H (H2H2 c ) = (H2H2+)(H2H2) with Hc a constant and H stable critical points of the equation. In this way, this simple model demonstrates that quantum efects may, by themselves, exibit stable de Sitter phases even without an introduction of a cosmological constant by hand. Althoug in a qualitative way, such result shows that, when dealing with the backreaction issue, a careful analysis of the quantization procedures is important for the analysis of cosmological efects of models of quantum field theories in curved spacetimes. (AU)