Beyond Moments: Robustly Learning Affine Transformations with Asymptotically Optimal Error

ACO Student Seminar
Friday, April 21, 2023 - 1:00pm for 1 hour (actually 50 minutes)
Skiles 005
He Jia – Georgia Tech CS – hjia36@gatech.edu
Abhishek Dhawan

We present a polynomial-time algorithm for robustly learning an unknown affine transformation of the standard hypercube from samples, an important and well-studied setting for independent component analysis (ICA). Total variation distance is the information-theoretically strongest possible notion of distance in our setting and our recovery guarantees in this distance are optimal up to the absolute constant factor multiplying the fraction of corruption. Our key innovation is a new approach to ICA (even to outlier-free ICA) that circumvents the difficulties in the classical method of moments and instead relies on a new geometric certificate of correctness of an affine transformation. Our algorithm is based on a new method that iteratively improves an estimate of the unknown affine transformation whenever the requirements of the certificate are not met.