科学研究
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2023.08.14
Inferred stellar parameters from 220 million XP spectra using an empirical forward model
Gaia data release 3 (GDR3) provides a trove of 220 million low-resolution BP/RP (XP) fluxcalibrated spectra. In order to properly exploit the XP spectra, we need to accurately model them as a function of stellar type, extinction and distance. We build a machine-learning model based on the subset of XP stars with LAMOST LRS counterparts, whose stellar types are precisely determined by the higher...
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2023.08.11
KiDS-1000: Cosmology with improved cosmic shear measurements
Weak gravitational lensing by large-scale structure, also known as cosmic shear, plays a crucial role in modern cosmology, powerfully probing the Universe's matter distribution. Interestingly, recent cosmic shear results from the KiDS, DES, and HSC surveys show an intriguing discrepancy with Planck's CMB observations concerning the amplitude of matter fluctuations. In this talk, I will discuss ...
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2023.07.28
Towards Optimal Inference of Cosmological Large Scale Structures with Neural Quantile Estimation
Traditional analysis of cosmological Large Scale Structures assumes that the likelihood is Gaussian, which unfortunately is not optimal and may even be biased in the non linear regime. Simulation Based Inference (SBI), also known as Likelihood Free Inference or Implicit Likelihood Inference, directly models the Bayesian optimal posterior, but typically needs a large number of simulations to con...
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2023.07.26
Modeling dwarf galaxy formation with UniverseMachine
Dwarf galaxies provide unique and rich constraints on galaxy formation and the nature of dark matter. However, the galaxy-halo mass connection at these low-masses still have a lot of uncertainty. With an influx of newly discovered dwarfs near and far, it is becoming increasingly important to place dwarf galaxies in a cosmological context and model their evolution in a self-consistent way. I wi...
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2023.07.24
Invasion of Alien Planet
This talk is on dynamics of the solar system, we show strong evidence that an alien planet once invaded our solar system. There is a long unsolved mystery concerning a group of asteroids called Jupiter Trojans. Mathematically, there are two symmetric relative equilibrium points for the Sun-Jupiter system, L4 and L5. However, there is a large difference in numbers of observed asteroids: L4 has 6...
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