Me calling Yi Lai, golden gate bridge.
Angxiu Ni (pronounces as "ang sh-you knee")
Assistant professor,
Qiu Zhen College and YMSC, Tsinghua University.
E-mail: niangxiu at tsinghua dot edu dot cn
Assistant professor, math of UC Irvine, starting fall 2024.
Recent
The adjoint shadowing lemma for discrete and contiuous-time hyperbolic systems is accepted at Nonlinearity.
I and Yao Tong extend the equivariant divergence formula to continuous-time.
I developed a 'no-propagate' algorithm; this might the missing piece to overcome non-hyperbolicity.
The theory and algorithm paper on the equivariant divergence formula are accepted at J. Stat. Phys. and SIADS.
I differentiate chaos by ergodic theorem formulas and Monte-Carlo algorithms (when dynamics is given, this means to sample by a long orbit).
I gave the pointwisely defined (this means having no exponentially exploding terms and no intermediate distributions that are not functions) linear response formula for hyperbolic system.
I developed the fastest algorithms for the parameter-derivative of long-time-average statistics.
More specifically,
1. Fast tangent response formula, equivariant divergence formula, and algorithms.
2. No-propgate algorithms, which is a long-time variant of the likelihood-ratio trick in random/statistics context.
3. Adjoint theories and algorithms, backpropagation under gradient explosion.
4. Non-intrusive shadowing algorithms.
I am also interested in the numerical interaction with chaos in all fields, such as fluids, geophysics, inference, data assimilation, and machine learning.
Teaching, Spring 2024
Computational probability, YMSC.
Misc.
Curriculum vitae
I got my PhD from
UC Berkeley math and did a postdoc at PKU BICMR.
I have been mentored by
John Strain,
Pingwen Zhang,
Mark Pollicott.
Previous Teaching