The first stars formed a few hundred million years after the Big Bang, when the Universe was only a small fraction of its present age. Their radiation transformed the previously cold and neutral... Show moreThe first stars formed a few hundred million years after the Big Bang, when the Universe was only a small fraction of its present age. Their radiation transformed the previously cold and neutral hydrogen that filled intergalactic space into the hot and ionised cosmic plasma that is observed today. This milestone in the history of the Universe is called the epoch of reionisation. Much about reionisation is still unknown. Computer simulations are one of the most promising theoretical tools to study reionisation. The wealth of high-quality data that will soon be provided by the next generation of telescopes, specifically designed to observe the reionisation event, make it a particularly exciting time to perform such simulations. The thesis "Simulating Cosmic Reionisation" presents TRAPHIC, a novel method to include the transport of ionising radiation emitted by the first stars in simulations of reionisation. TRAPHIC (TRAnsport of PHotons In Cones) is one of the first of a new type of radiative transfer methods that allow the accurate and efficient computation of the growth of ionised regions in representative models of the Universe that contain hundreds of millions of stars. First simulations that employ TRAPHIC on the Dutch national supercomputer Huygens demonstrate the importance of the concepts that underly its design. Show less
Dark matter assembles to form massive halos, attracting gas particles that coalesce to form stars, and the photons produced by these sources are sent into the void. An accurate description of the... Show moreDark matter assembles to form massive halos, attracting gas particles that coalesce to form stars, and the photons produced by these sources are sent into the void. An accurate description of the transport of particles is therefore the essential ingredient for understanding how the Universe evolved into its present form. Of all these transport processes, the transfer of radiation is the most elusive: the non- locality and high-dimensionality of the problem currently put realistic simulations out of reach. In this thesis, we present a novel approach to this transport problem, combining methods from mathematics and statistical physics in a practical computer code. Its speed and versatility allow us, for the first time, to make realistic simulations in radiative gas dynamics and in cosmology. Because of the general mathematical/physical character of our methods, we expect them to be useful for transport phenomena in general. Show less
