Kiril Maltsev (Germany)
kiril.maltsev @ h-its.org
Stellar evolution emulators
Stars are self-gravitating bodies that convert gravitational contraction work into radiation heat, and whose dominant internal energy source originates from nuclear fusion. They form in the gravitational collapse of gigantic gaseous nebula, and burn successively heavier elements as they undergo a sequence of evolutionary phases, governed by an exciting interplay of gravity and thermodynamics, quantum nuclear and particle physics, and hydrodynamics. Stars end their lives by transformation into compact objects, or in violent supernova explosions tearing them apart. Massive stars become large, shine bright, and die young. Though particularly their late evolutionary stages are not well understood.
There is no general analytical solution to the coupled nonlinear differential equations effectively describing stellar evolution. MESA is a powerful numerical tool for constructing stellar models. However, many astronomical applications -such as stellar population synthesis- require an efficient yet reliable way to determine the outcome of single star and binary star evolution. A central task of my PhD project is to enhance the deterministic stellar evolution modeling by methods of probabilistic forecasting: we aim to interpolate stellar evolution tracks, pre-computed with MESA, by machine learning algorithms. These emulators trace stellar variables such as core density, surface gravity and luminosity, over the course of evolution, for a wide range of initial masses and metallicities. They increase predictive power of modeling while keeping the computational expenses low. The goal is that, aided by the stellar evolution emulators, we will be able to shed light on the question - given that a collapsing gas sphere has initial mass M and metallicity Z, what then is its most likely stellar evolution scenario, and compact remnant final state?
A side interest of my research concerns the foundation of black hole thermodynamics. In particular, the grounding of thermodynamic significance of heat, work, temperature and entropy in classical Kerr Black Holes and semi-classical Schwarzschild Black Holes.
Supervisor: Friedrich Roepke (HITS)