Thesis (M. Sc.)--York University, 2000. Graduate Programme in Physics and Astronomy. / Typescript. Includes bibliographical references (leaves 119-121). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pMQ56161.

Thesis (M. Phil.)--University of Hong Kong, 1987.

The effect of dust/gas heating and cooling is shown to have a significant effect on the process of clustered star formation. Compared to an isothermal simulation, a simulation with a more accurate description of the equation of state produces an order of magnitude fewer stars as well as stars of much greater mass. The energetics algorithm used to calculate the dust and gas temperature includes the radiative heating of dust, dust-gas collisional heating/cooling, cosmic-ray heating, and molecular cooling. It uses DUSTY, a spherical continuum radiative transfer code, to model the dust temperature distribution around young stellar objects with various luminosities and surrounding gas and dust density distributions. The gas temperature is then determined by assuming energy balance. Before the complete energetics algorithm is included in a simulation, first only the dust heating component is included. The gas temperature is then set solely by the dust temperature. The resultant mass functions of our simulations which include heating are compared to those which assume an isothermal equation of state. We find that including dust heating severely limits star formation; we form at least an order of magnitude fewer objects when we include dust heating compared to an isothermal simulation. The mass functions from our simulations which include heating are much more similar than the mass functions from our isothermal simulations to the observed mass functions, in that they are able to form high-mass stars (M [> subscript tilde] 10M[solar mass]). The distribution of the high-mass objects is well-approximated by the Salpeter initial mass function. Including the complete energetics algorithm in a simulation produces results similar to a simulation with only dust heating. Both simulations have similar density profile parameters. The mass accretion, mass, and luminosity evolution of the sinks is also similar. The average temperature, however, is cooler than the simulation with only dust heating. We form fewer objects comparatively and are still unable to form enough low and intermediate-mass objects to replicate the observed mass function. This may be an effect of small number statistics, or possibly physical processes that are not considered in this work. / text

The inflationary paradigm has become widely accepted as an accurate framework in which to describe the physics of the early universe, due both to the conceptual advantages of the idea and the agreement of its predictions with observational data. However, it remains to be determined which of the many detailed theories of inflation correctly describe the universe in which we live. Any such theory faces the challenge of making accurate predictions which agree with observation while also fitting consistently into a theory of high energy physics. Within this challenge there exists the great opportunity to constrain speculative models of fundamental physics. Inflation thereby provides an observational window into theories conventionally thought to be unreachable by experiment. Measurements of anisotropies in the cosmic microwave background radiation and the distribution of large scale structure have proved to be invaluable tools to probe inflation. There has been recent interest in examining the deviations from gaussianity in the statistics of the observed fluctuations. These higher order statistics, if conclusively discovered, stand to teach us a great deal about inflation. Forthcoming data including improved measurements of the cosmic microwave background temperature and polarization will provide additional means to investigate the inflationary era. It is important to understand precisely what impact inflation has had on the universe we observe and thus understand precisely what observation can tell us about inflation and how it may fit into a fundamental theory of physics. We will show the conditions under which the cosmological correlation functions generated during inflation are conserved, and thus identify the conditions which allow us to use observations today to learn about inflation. We first prove a general result which applies only to the leading approximation of the correlation functions, and then we discuss how to treat the additional complications that come with subleading corrections. Next, we will discuss the observational implications of achieving the conditions for conservation for a particular class of inflationary models. Lastly, we discuss one example of how observations can be used to probe non-inflationary physics beyond the standard cosmological model. / text

published_or_final_version / Physics / Doctoral / Doctor of Philosophy

published_or_final_version / Physics / Master / Master of Philosophy

Not available / text

published_or_final_version / Physics / Master / Master of Philosophy

No description available.

No description available.