Veranstaltungen

We provide necessary and sufficient conditions for the chi-squared and normal approximations of Pearson's chi-squared statistics for the test of independence and the goodness-of- t test, as well as necessary and sufficient conditions for the normal approximation of the likelihood ratio and Hellinger statistics, when the cell probabilities of the multinomial data are in general pattern and the dimension diverges with the sample size. A cross-sample chi-squared statistic for testing independence applies to two-way contingency tables with diverging dimensions. A degrees-of-freedom adjusted chi-squared approximation applies continuously throughout the high-dimensional regime and matches Pearson's chi-squared statistic in both the mean and variance. Specific examples are provided to demonstrate the asymptotic normality of the three types of test statistics when the classical regularity conditions for the chi-squared and normal approximations are violated. Simulation results demonstrate that the chi-squared and normal approximations are more robust for the likelihood ratio and Hellinger statistics, compared with Pearson's chi-squared statistics. This talk is based on joint work with Chong Wu and Yisha Yao.

Wilson loop amplitudes are a central concept in gauge theories, offering a way to study the behavior of particles and their interactions with gauge fields as they move along closed paths in spacetime. In this talk, we give a mathematical description of Wilson loop amplitudes in 5D gauge theory. This description will lead to conjectures about structures of Gromov-Witten invariants of some compact semi-Fano threefolds. We will give some evidence for these conjectures. This is a work in progress with Shuai Guo and Xin Wang.