Speaker:	Leung Shing Chi (The Chinese University of Hong Kong)
Title:	Effects of non-self-annihilating dark matter on stellar objects
Date (JST):	Tue, Mar 10, 2015, 12:00 - 13:00
Place:	Seminar Room B
Abstract:	Dark matter is a major constituent of the universe which accounts for more than 80% of mass in the matter-sector. It plays an important role in the evolution of the universe including the formation of large-scale structure, galaxy formation and so on. Despite its wide influence, dark matter remains mysterious that most of its fundamental properties, including the particle mass and scattering cross sections, are unknown or not well constrained. Numerous methods, including direct detections or indirect detections, namely by predicting or probing the influences of dark matter in the astrophysical context, are proposed in order to search for its trace of interactions with ordinary matter. On the other hand, we have a much better understanding about stars. The current framework of astrophysics has successfully explained many observed properties of stars. However, most theoretical studies of stellar objects do not take the effects of dark matter into account. In fact, in view of the dark matter abundance, it is possible that a significant amount of dark matter co-exists inside stars in forms of admixture, especially in early stars or stars located inside a dark matter halo. Therefore, for a more comprehensive picture of stellar astrophysics, there is still a need in understanding the impacts of dark matter admixture on stars. In this seminar, we discuss the indirect detection methods of dark matter by considering its possible effects on different types of stellar objects, including main-sequence stars, white dwarfs and neutron stars. We treat the dark matter as a non-self-annihilating ideal degenerate Fermi gas which interacts with ordinary matter through gravity. We study the influences of dark matter admixture on the stellar properties, from static properties such as the mass-radius relation and oscillation modes, to dynamical properties such as time evolutions of explosion and collapse scenarios. For a class of dark matter, we find novel results including a new type of compact stars, a new class of oscillation modes and so on. Detections of these mentioned objects can provide strong hints on the properties of dark matter particle including its particle mass. Also, such dark matter admixture may be an explanation to of unusual stellar observations, for example ultra-compact neutron stars or sub-luminous Type-Ia supernovae.

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