The manifestations of thermal instabilities in accretion discs

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Accretion discs are found in a large number of astrophysical situations. They form when matter falls under gravity towards a central, often compact, body. Due to angular momentum in the material, it settles into a disc around the central body. Viscous forces in the disc cause material to move inwards and accrete onto the central object.A simplified analytical theory of these discs suggests that they should be unstable to thermal fluctuations (ie they should catastrophically heat or cool). There is no indication in observations that this happens in nature, and the reason for this is still poorly understood.We aim to explore this problem, starting with extensions to the simplified analytical theory involving stochastic processes. Our eventual plan is to construct large scale computer simulations which will enable us to study these phenomena (or lack thereof) in detail.