1998年，通过对Ia型超新星的观测，两个研究组各自独立地发现了宇宙正在经历加速膨胀；由于这个伟大的发现，三位美国科学家获得了2011年的诺贝尔物理学奖。16年过去了，这个结论已得到了越来越多其他宇宙学观测的证实，但Ia型超新星依然是研究宇宙加速膨胀的最重要最有力的工具之一。目前观测到的超新星样本数已达到到几百颗。未来10年的观测项目，如LSST，将把超新星样本数提高到几万。随着样本数的增加，超新星的统计误差将变得越来越小，而它的系统误差将变得越来越重要。如何分析处理超新星的系统误差，已成为国际主要超新星观测组目前最关心的问题。系统误差源于很多因素，包括测光、校准及超新星识别的误差，超新星物理性质的内禀性改变，宿主星系消光，引力透镜效应等。本项目主要关注超新星物理性质的内禀性改变，尤其是亮度-色变参数β和内秉离散σ可能存在的演化。我们还将研究这些因素对宇宙学参数评估的影响。

In 1998, via the observations on type Ia supernovae (SNIa), two groups independently discovered that our universe is undergoing an accelerated expansion; because of this great discovery, three American scientist won the 2011 Nobel Prize in Physics. 16 years has past, this conclusion has been confirmed by more and more other cosmological observations, but SNIa is still one of the most important and powerful tools to study the cosmic acceleration. The current number of SNIa sample is several hundred. The observational projects of future ten years, such as LSST, will increase the number of SNIa sample to tens of thousands. Along with the increase of sample number, the statistical errors will become smaller and smaller, while the systematic errors will become more and more important. How to analyze and deal with the systematic uncertainties of supernovae has already become the most concerned issue for the mainstream supernovae research groups. The systematic errors come from various factors, including the errors in the photometry, the calibration, the identification of SNIa, the intrinsic variation of physical properties of SNIa, the host-galaxy extinction, the gravitational lensing effect, and so on. This project focus on the intrinsic variation of physical properties of SNIa, in particular the possible evolution of color-luminosity parameter β and intrinsic scatter σ. We will also study the effects of theses factors on the cosmological parameter estimation.