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math.ST2025
Optimal Bounds for Tyler's M-Estimator for Elliptical Distributions
Lap Chi Lau, Akshay Ramachandran
A fundamental problem in statistics is estimating the shape matrix of an Elliptical distribution. This generalizes the familiar problem of Gaussian covariance estimation, for which…
quant-ph2025
Computational Aspects of the Trace Norm Contraction Coefficient
Idris Delsol, Omar Fawzi, Jan Kochanowski +1
We show that approximating the trace norm contraction coefficient of a quantum channel within a constant factor is NP-hard. Equivalently, this shows that determining the optimal su…