Thomas Royen (born 6 July 1947) is a retired German professor of statistics who has been affiliated with the University of Applied Sciences Bingen.
Royen came to prominence in the spring of 2017 for a relatively simple proof for the Gaussian Correlation Inequality (GCI), a conjecture that originated in the 1950s, which he had published three years earlier without much recognition.
After attaining his PhD in 1975 with a thesis called Über die Konvergenz gegen stabile Gesetze (On Convergence Against Stable Laws), he worked as a Wissenschaftlicher Assistent at Dortmund University's institute for statistics.
[4] On 17 July 2014, a few years after his retirement, when brushing his teeth, Royen had a flash of insight: how to use the Laplace transform of the multivariate gamma distribution to achieve a relatively simple proof for the Gaussian correlation inequality, a conjecture on the intersection of geometry, probability theory and statistics, formulated after work by Dunnett and Sobel (1955) and the American statistician Olive Jean Dunn (1958),[5] that had remained unsolved since then.
[9] A 2017 article by Natalie Wolchover about Royen's proof in Quanta Magazine resulted in greater academic and public recognition for his achievement.