Citation
Jacobs, Kenneth Charles (1969) Bianchi type I cosmological models. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/KSSQR708. https://resolver.caltech.edu/CaltechETD:etd10162002080822
Abstract
NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. This thesis begins with a brief review of observations of cosmological interest and with a sketch of the "standard" spatially homogeneous and isotropic cosmological models of our Universe that are currently in vogue. Following this introduction we investigate in great detail anisotropic cosmologies and cosmological models of Bianchi Type I. Our primary goal is to understand the consequences of expansion anisotropies in the general relativistic, hot bigbang theory of cosmology. We use the Einstein field equations with vanishing cosmological constant, and Maxwell's equations, to study the temporal evolution of anisotropic Bianchi Type I cosmologies. These cosmologies are spatially homogeneous, but anisotropic; and they have no rotation. We consider only cosmologies with the "flat", diagonal, Bianchi Type I metric ds[superscript 2]  dt[superscript2]  A[superscript 2](t)dx[superscript 2]  B[superscript 2](t)dy[superscript 2]  C[superscript 2](t)dz[superscript 2]. We begin by studying the general properties of Bianchi Type I cosmologies. Then we consider the stressenergy tensor for masslessparticle gases (either degenerate or nondegenerate) which decouple from thermal equilibrium and become freelypropagating in our diagonal Bianchi Type I metric. We investigate the dynamical effects of anisotropic neutrino stresses, and we show how neutrino viscosity damps out most of the existing expansion anisotropies when neutrinos decouple. Finally, we elucidate the structure and properties of the Einstein field equations for anisotropic Bianchi Type I cosmologies by deriving a large number of analytical and numerical solutions to these equations. Our stressenergy tensor consists, in general, of perfectfluid matter with the barotropic equation of state p[subscript m] = [gamma] [rho][subscript m] (0 [<=] [gamma] [<=] 1), and a uniform comoving magnetic field, with energydensity [rho][subscript b], aligned along the zaxis. We first consider the PERFECTFLUID case where [rho][subscript b] = 0. We find the general analytical solution (for all [gamma]), and construct semirealistic cosmological models of our Universe using this solution. Then we consider the PERFECTFLUIDMAGNETIC case where [rho][subscript b] [is not equal to] 0. We derive several analytical solutions, find the behavior near the initial physical singularity for the remaining cases, and study those remaining cases by numerical integration of the field equations. We then consider semirealistic PERFECTFLUIDMAGNETIC cosmological models of our Universe. In our semirealistic cosmological models we study the possible effects of expansion anisotropies and of a uniform primordial magnetic field upon the following: (a) the type of initial physical singularity, (b) the thermal history and temporal evolution of our Universe, (c) primordial element formation, (d) the time when expansion anisotropies become small, and (e) the temperature isotropy of the observed 2.7[degrees]K cosmic microwave radiation.
Item Type:  Thesis (Dissertation (Ph.D.)) 

Degree Grantor:  California Institute of Technology 
Division:  Physics, Mathematics and Astronomy 
Major Option:  Physics 
Thesis Availability:  Public (worldwide access) 
Research Advisor(s): 

Group:  TAPIR, Astronomy Department 
Thesis Committee: 

Defense Date:  1 October 1968 
Record Number:  CaltechETD:etd10162002080822 
Persistent URL:  https://resolver.caltech.edu/CaltechETD:etd10162002080822 
DOI:  10.7907/KSSQR708 
Default Usage Policy:  No commercial reproduction, distribution, display or performance rights in this work are provided. 
ID Code:  4107 
Collection:  CaltechTHESIS 
Deposited By:  Imported from ETDdb 
Deposited On:  16 Oct 2002 
Last Modified:  10 Mar 2020 23:39 
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