3 papers
stat.CO2026
The Snake Algorithm: A Rejection-Free Sampler for Binary Matrices with Fixed Margins
Zipei Nie, Guanyang Wang, Peng Zhang
We study uniform sampling of binary matrices with fixed row and column sums, a recurring problem in ecological null models, Rasch-model testing, network analysis, and combinatorics…
math.GR2026
Torsion in asymptotic cones of free groups
Jarek Kędra, Assaf Libman, Zipei Nie
We prove that the asymptotic cone of any non-abelian free group equipped with the bi-invariant word metric has elements of order 2.
math.PR2026
On Feige's conjecture
Zipei Nie, Jiaye Wei
We present a short proof of Feige's conjecture: for independent nonnegative random variables with expectation one, the probability that their sum is less than is at least…