M.Sc Student | Muhammad Akashi |
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Subject | Nonlinear Coupled Cosmological Perturbations |

Department | Department of Physics |

Supervisor | Full Professor Nusser Adi |

According to the standard cosmological paradigm, the universe is predominantly made of dark matter. The gaseous baryonic component from which the luminous structure form, contains only sixteen percent of the mass. Only on large scales, this gaseous component is an honest tracer of the large scale distribution of the dark matter. On small scales where pressure effects of the collisional baryonic gas become important, its distribution may deviate from that of the dark matter.

This Thesis is concerned with modeling the gas distribution and its relation to that of the dark matter. A full treatment of this problem requires high resolution three dimensional hydrodynamical simulation. These simulations are very costly and the available computing power has only begun to border the necessary numerical resolution. In this thesis we adopt the strategy of modeling the gas distribution in one spatial dimension. To do that, we have developed a one dimensional numerical hydrodynamical code, which includes dark matter and baryonic gas.

Numerical solutions for the evolution of cosmological non-linear density perturbations in the baryonic gas and collisionless dark matter are derived.

They are obtained assuming _{}, the universe
is flat without cosmological constant, one dimensional box, with low continuous
heating and high continuous heating and initial heating. Before the heating the
medium is cold and the baryonic and dark matter trace the same density and
velocity fields.

In this work we have obtained a
parametric form of the gas density power spectrum in terms of that of the dark
matter, _{} .

We see that the smoothed dark matter density fluctuations goes well as the gas density fluctuations in all the cases we have investigated, where in the linear regime both of them should be the same.

The gas density fluctuations go after the dark matter density fluctuations according to the heat we put in the system.