Physics Student Conference Program and Information
◎Be Neutrinos- how seemingly insignificant ghost particles have changed the universe
Neutrinos are the least interactive and understood among the known elementary particles. Some 10^14 solar neutrinos pass through your body every second, with no consequences. Surprisingly, such ghost-like particles play an important role in shaping the universe. The speaker will discuss why neutrinos are essential for explosions of massive stars- important for spreading of elements in the universe, and why we exist at all. He will also introduce neutrinos’ roles in the evolution of the universe, and a plan for Hong Kong researchers to measure neutrino properties using cosmological observation.
◎From Dark Matter to Galaxies with Convolutional Neural Networks
Cosmological simulations play an important role in the interpretation of astronomical data, in particular in comparing observed data to our theoretical expectations. However, to compare data with these simulations, the simulations in principle need to include gravity, magneto-hydrodyanmics, radiative transfer, etc. These ideal large-volume simulations(gravo-magneto-hydrodynamical) are incredibly computationally expensive which can cost tens of millions of CPU hours to run. In this paper, a deep learning approach is proposed to map from the dark-matter-only simulation(computationally cheaper) to the galaxy distribution(from the much costlier cosmological simulation). The main challenge of this task is the high sparsity in the target galaxy distribution: space is mainly empty. The speaker and his team propose a cascade architecture composed of a classification filter followed by a regression procedure. They show that their result outperforms a state-of-the-art model used in the astronomical community, and provides a good trade-off between computational cost and prediction accuracy.
講者：Yip Hoi Tung
◎How dark matter will affect different celestial bodies
Over the few decades, many theories were established for different kinds of celestial bodies. However, due to recent observations, it is believed that more than a quarter of our universe are made of dark matter. Although the nature of dark matter is still a mystery nowadays, we still want to see how dark matter will affect different parameters of celestial bodies(e.g. density, pressure, velocity) by making some assumptions on dark matter.
◎Dark Matter Admixed White Dwarfs and Thermonuclear Explosion
Astronomers believe that the matter content of the universe is dominated by dark matter(DM), which are weakly interacting and massive, but their properties are largely unknown. The search for astronomical DM, although difficult, remains one of the major goals in the astrophysics particle physics. There is recent rising interest in DM admixed stellar objects, such as stars and compact stars. In particular, DM admixed white dwarfs(DMAWD) and their thermonuclear explosions were one of the possible models for sub-luminous Type Ia supernovae. In this talk, a model of DMAWD with DM as ideal fermi gas would be presented. Numerical calculation of their effect to the equilibrium structure of DMAWD, and the simulations of their thermonuclear explosions are presented and briefly discussed. It is found that DMAWD with DM particles mass around 0.1GeV could produce DMAWD with comparable order of NM and DM mass and radius. The NM with mass usually lower than that of typical Type Ia supernovae, could produce less Nickel-56 under thermonuclear explosions, and hence could be a possible model of sub-luminous type Ia supernovae.
講者：Chan Ho Sang