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University of KwaZulu-Natal

1.
Bogadi, Robert Sacha.
Relativistic thermodynamics of *radiating* *stars*.

Degree: 2016, University of KwaZulu-Natal

URL: http://hdl.handle.net/10413/14876

In this research, on the topic of relativistic thermodynamics of radiating stars, the
following three case studies are investigated:
Gravitational collapse in spacially isotropic coordinates { The nature of a dissipative
collapse process of a spherically symmetric star which has been perturbed into a
dynamical state from an initial static con guration is studied. The collapse process
involves dissipation of energy in the form of a radial heat flux. The perturbation in the
density and pressure profi les are such that the star is always close to hydrostatic equilibrium.
The temperature profi les are studied using a causal heat transport equation.
Radiating collapse in the presence of anisotropic stresses { The effect of anisotropic
stresses are investigated for a collapsing fluid sphere dissipating energy in the form of
a radial flux. The collapse process starts from an initial static sphere described by
the Bowers and Liang solution, and then proceeds until the time of formation of the
horizon. We fi nd that the surface redshift increases as the stellar fluid moves away
from isotropy. The evolution of the temperature pro les is analysed by employing a
causal heat transport equation of the Maxwell-Cattaneo form. Both the Eckart and
causal temperatures are enhanced by anisotropy at each interior point of the stellar
con guration.
The influence of an equation of state during radiative collapse { A linear equation
of state is imposed on a static con guration which undergoes radiative gravitational
collapse. Various values of the equation of state parameter allow descriptions of di erent
matter content from classical stars to dust and also dark energy stars. The physical
parameters are shown to behave in a meaningful and realistic manner.
*Advisors/Committee Members: Govender, M. (advisor), Maharaj, S. D. (advisor).*

Subjects/Keywords: Relativistic thermodynamics.; Radiating stars.; Gravitational collapse.

Record Details Similar Records

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^{th} Edition):

Bogadi, R. S. (2016). Relativistic thermodynamics of radiating stars. (Thesis). University of KwaZulu-Natal. Retrieved from http://hdl.handle.net/10413/14876

Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^{th} Edition):

Bogadi, Robert Sacha. “Relativistic thermodynamics of radiating stars.” 2016. Thesis, University of KwaZulu-Natal. Accessed July 15, 2019. http://hdl.handle.net/10413/14876.

Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^{th} Edition):

Bogadi, Robert Sacha. “Relativistic thermodynamics of radiating stars.” 2016. Web. 15 Jul 2019.

Vancouver:

Bogadi RS. Relativistic thermodynamics of radiating stars. [Internet] [Thesis]. University of KwaZulu-Natal; 2016. [cited 2019 Jul 15]. Available from: http://hdl.handle.net/10413/14876.

Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Bogadi RS. Relativistic thermodynamics of radiating stars. [Thesis]. University of KwaZulu-Natal; 2016. Available from: http://hdl.handle.net/10413/14876

Not specified: Masters Thesis or Doctoral Dissertation

University of KwaZulu-Natal

2.
Brassel, Byron P.
Dynamics of *radiating* *stars* in the strong gravity regime.

Degree: 2017, University of KwaZulu-Natal

URL: http://hdl.handle.net/10413/15649

We model the dynamics of a spherically symmetric radiating dynamical star, emitting
outgoing null radiation, with three spacetime regions. The local internal atmosphere
is a two-component system consisting of standard pressure-free, null radiation and an
additional string
fluid with energy density and nonzero pressure obeying all physically
realistic energy conditions. The middle region is purely radiative which matches to
a third region which is the Schwarzschild exterior. A large family of solutions to the
field equations are presented for various realistic equations of state. A comparison of
our solutions with earlier well known results is undertaken and we show that all these
solutions, including those of Husain, are contained in our family. We then generalise
our class of solutions to higher dimensions and consider the effects of diffusive transport
We also study the gravitational collapse in the context of the cosmic censorship
conjecture. We outline the general mathematical framework to study the conditions on
the mass function so that future directed nonspacelike geodesics can terminate at the
singularity in the past. Mass functions for several equations of state are analysed using
this framework and it is shown that the collapse in each case terminates at a locally
naked central singularity. These singularities are strong curvature singularities which
implies that no extension of spacetime through them is possible. These results are then
extended to modified gravity. We establish the result that the standard Boulware-Deser
spacetime can radiate. This allows us to model the dynamics of a spherically symmetric
radiating dynamical star in ve-dimensional Einstein-Gauss-Bonnet gravity with
three spacetime regions. Finally, the junction conditions are derived entirely in five dimensional
Einstein-Gauss-Bonnet gravity via the matching of two spacetime region
leading to a model for a radiating star in higher order gravity.
*Advisors/Committee Members: Maharaj, Sunil D. (advisor), Goswami, Rituparno. (advisor).*

Subjects/Keywords: Gravity.; Radiating stars.; Equations.; Black holes.

Record Details Similar Records

❌

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^{th} Edition):

Brassel, B. P. (2017). Dynamics of radiating stars in the strong gravity regime. (Thesis). University of KwaZulu-Natal. Retrieved from http://hdl.handle.net/10413/15649

Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^{th} Edition):

Brassel, Byron P. “Dynamics of radiating stars in the strong gravity regime.” 2017. Thesis, University of KwaZulu-Natal. Accessed July 15, 2019. http://hdl.handle.net/10413/15649.

Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^{th} Edition):

Brassel, Byron P. “Dynamics of radiating stars in the strong gravity regime.” 2017. Web. 15 Jul 2019.

Vancouver:

Brassel BP. Dynamics of radiating stars in the strong gravity regime. [Internet] [Thesis]. University of KwaZulu-Natal; 2017. [cited 2019 Jul 15]. Available from: http://hdl.handle.net/10413/15649.

Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Brassel BP. Dynamics of radiating stars in the strong gravity regime. [Thesis]. University of KwaZulu-Natal; 2017. Available from: http://hdl.handle.net/10413/15649

Not specified: Masters Thesis or Doctoral Dissertation