Yuankai Guo

An atom obstruction to stochastic non-diversification

In models with infinite mean, weighted averages of independent risks can stochastically dominate the underlying marginal distribution. This paper studies the class D⁻ of probability measures on the real line for which this non-diversification phenomenon holds across all finite co...

The cardinality spectrum of quantum Latin squares of order seven

This deposit contains the manuscript, exact algebraic certificates, and complete Lean 4 formalization settling the cardinality spectrum of quantum Latin squares of order seven. We show that the possible cardinalities for order seven are exactly {7, 9, 10, ..., 49}, with 8 exclude...

A Counterexample to a Problem of Pommerenke on Convex Functions in the Class Σ

A Counterexample to a Problem of Pommerenke on Convex Functions in the Class Σ This preprint studies Problem 6.10 in W. K. Hayman and E. F. Lingham's Research Problems in Function Theory. The paper presents an explicit construction involving the functions \[ F(z)=z+\alpha z^{-1},...